American Thoracic Societv
Guidelines for Methacholine and Exercise Challenge
Testing-1999
T HIS O FFICIAL STA.TEMENT OF THE A MERICAN THORACIC SOCIETY W AS ADORED BY THE ATS BOARD OF D IRECTORS , J ULY 1999

I. Purpose and Scope
II. Methacholine Challenge Testing
A. Indications
B. Contraindications
C. Technician Training/Qualifications
D. Safety
E. Patient Preparation
F. Choice and Preparation of Methacholine
G. Dosing Protocols
1. Two-Minute Tidal Breathing Dosing Protocol
2. Five-Breath Dosimeter Protocol
H. Nebulizers and Dosimeters
I. Spirometry and Other End-point Measures
J. Data Presentation
K. Interpretation
III. Exercise Challenge
A. Indications
B. Contraindications and Patient Preparation
C. Exercise Challenge Testing
D. Assessing the Response
References
Appendix A: Sample Methacholine Challenge Test Consent
Form
Appendix B: Sample Methacholine Challenge Pretest Questionnaire
Appendix C: Sample Report Format
Appendix D: Equipment Sources

The bronchial challenge tests chosen for review are the twomost widely used, with enough information in the literature toevaluate their utility. Of the two, methacholine challenge testing is better established; a number of aspects in the exercise
challenge protocol will benefit from further evaluation. We do
not cover specific challenges with allergens, drugs, or occupational sensitizers, and recommend that such tests be performed
only in laboratories with considerable experience in their techniques. For more extensive details or other challenge procedures the reader is referred to previously published guidelines
for bronchial challenge testing (l-5) and reviews on the general topic of BHR (6-9).
As with other American Thoracic Society (ATS) statements
on pulmonary function testing, these guidelines come out of aconsensus conference. The basis of discussion at the committee’s
September 1997 meeting was a draft prepared by three members(P.E., C.I., and R.C.). The draft was based on a comprehensive
Medline literature search from 1970 through 1997, augmented
by suggestions from other committee members. The final recommendations represent a consensus of the committee. For issues on which unanimous agreement could not be reached, theguidelines reflect both majority and minority opinions.
The committee recommends that the guidelines be reviewed
in 5 years and, in the meantime, encourages further researchin the areas of controversy.
II. METHACHOLINE CHALLENGE TESTING
A. Indications

I. PURPOSE AND SCOPE
This statement provides practical guidelines and suggestions
for methacholine and exercise challenging testing. Specifically, it reviews indications for these challenges, details factorsthat influence the results, presents brief step-by-step protocols, outlines safety measures, describes proper patient preparation and procedures, provides an algorithm for calculating
results, and offers guidelines for clinical interpretation of results. The details are important because methacholine and exercise challenge tests are, in effect, dose-response tests anddelivery of the dose and measurement of the response must be
accurate if a valid test is to be obtained. These guidelines are
geared to patients who can perform good-quality spirometry
tests; they are not appropriate for infants or preschool children. They are not intended to limit the use of alternative protocols or procedures that have been established as acceptable
methods. We do not discuss the general topic of bronchial hyperresponsiveness (BHR).

Am J Respir Crit Care Med Vol 161. pp 309-329, 2000
Internet address: www.atsjournals.org

Methacholine challenge testing is one method of assessing airway responsiveness. Airway hyperresponsiveness is one of thefeatures that may contribute to a diagnosis of asthma. It mayvary over time, often increasing during exacerbations and decreasing during treatment with antiinflammatory medications.
Methacholine challenge testing (MCT) is most often considered when asthma is a serious possibility and traditional methods, most notably spirometry performed before and afteradministration of a bronchodilator, have not established oreliminated the diagnosis. Symptoms that suggest asthma include wheezing, dyspnea, chest tightness, or cough in the following circumstances: (I) with exposure to cold air, (2) after
exercise, (3) during respiratory infections, (4) following inhalant exposures in the workplace, and (5) after exposure to allergens and other asthma triggers. A history of such symptoms
increases the pretest probability of asthma. The optimal diagnostic value of MCT (the highest combination of positive andnegative predictive power) occurs when the pretest probability of asthma is 30-70% (10). Methacholine challenge testingis more useful in excluding a diagnosis of asthma than in establishing one because its negative predictive power is greaterthan its positive predictive power.
Methacholine challenge testing is also a valuable tool in theevaluation of occupational asthma. Methacholine challenge

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testing is sometimes used to determine the relative risk of developing asthma, assess the severity of asthma, and assess response to asthma therapy although its clinical use in these areas has not been well established.
Rationale. Even asthma specialists cannot accurately predict MCT results in patients with an intermediate probabilityof asthma (I 1). The MCT has excellent sensitivity but mediocre positive predictive value for asthma (8). Most subjects withcurrent asthma symptoms will have BHR. However, bronchial
hyperresponsiveness is also seen in a wide variety of other diseases, including smoking-induced chronic airway obstruction(COPD), congestive heart failure (CHF), cystic fibrosis, bronchitis, and allergic rhinitis (12-14).
Because improvement in the clinical severity of asthma is
associated with improvement in airway responsiveness (1.5,16) clinical studies of asthma therapies often use change in airway responsiveness as an objective outcome measure (9, 1725). Sont and colleagues have demonstrated the efficacy of atreatment program that included measures of airway hyperreactivity in the management approach (26). However, we believe the routine use of MCT to examine patients with asthma
in a clinical setting should await further exploration of the utility of such testing.
B. Contraindications
The contraindications to methacholine challenge testing, summarized in Table 1, are all conditions that may compromise
the quality of the test or that may subject the patient to increased
risk or discomfort. They are identified in the pretest interview
or questionnaire. If contraindications are identified, theyshould be discussed with the physician who ordered the test or
the medical director of the laboratory before proceeding.
Rationale. Low FEV,. Occasional dramatic falls in FEV,
may occur during MCT and the risk of such events may be increased in individuals with low baseline lung function. Reduced lung function is a relative contraindication because theoverall risk of serious adverse events is small, even in patientswith asthma who have severe airway obstruction (27). The
level of lung function at which MCT is contraindicated is controversial. A baseline FEV, of < 1.5 L or < 60% predicted in
adults is proposed as a relative contraindication by Sterk andcoworkers (I) and Tashkin and coworkers (28). Half of 40 investigators polled in one study considered an FEV, of < 70%
predicted to be a contraindication (29); 20% used cutoff
points of 60% of predicted and 20% used 80% of predicted.
The Second National Asthma Expert Panel Report used an
FEV, < 65% predicted (30).
Airway obstruction. It is difficult to interpret a “positive”
methacholine challenge result when baseline spirometry shows
airway obstruction (a low FEV,/FVC and low FEV,), because

TABLE 1
CONTRAINDICATIONS FORMETHACHOLINE CHALLENGE TESTING
Absolute:
Severe airflow limitation (FEV, < 50% predicted or < 1 .O L)
Heart attack or stroke in last 3 mo
Uncontrolled hypertension, systolic BP > 200, or diastolic BP > 100
Known aortic aneurysm
Relative:
Moderate airflow limitation (FEV, < 60% predicted or < 1.5 L)
Inability to perform acceptable-quality spirometry
Pregnancy
Nursing mothers
Current use of cholinesterase inhibitor medication (for myasthenia gravis)

2000

airway responsiveness correlates strongly with the degree ofbaseline airway obstruction in COPD. In the presence of agood clinical picture for asthma, if baseline spirometry shows
airflow obstruction and there is a significant bronchodilator
response (> 12% and > 0.2-L increases in either FEV, or
FVC) the diagnosis of asthma is often confirmed and MCT isusually unnecessary.
Spirometry quality. An acceptable-quality methacholine
challenge test depends on the ability of the patients to perform
acceptable spirometric maneuvers. Patients who cannot perform acceptable spirometry tests in the baseline session should
perhaps be rescheduled or be tested using an end-point measure that is less dependent on patient effort.
Cardiovascular problems. A history of cardiovascular problems may also be a contraindication, depending on the problem. The additional cardiovascular stress of induced bronchospasm may precipitate cardiovascular events in patients withuncontrolled hypertension or recent heart attack or stroke. Induced bronchospasm causes ventilation-perfusion mismatching(31,32), which can result in arterial hypoxemia and compensatory changes in blood pressure, cardiac output, and heart rate
(33, 34). On the other hand, cardiac arrhythmia rates actually
fall during the performance of FVC maneuvers (35).
Pregnancy and nursing mothers. Methacholine is a pregnancy category C drug, meaning that animal reproductive studies have not been performed and it is not known whether it isassociated with fetal abnormalities. It is not known whether
methacholine is excreted in breast milk.
C. Technician Training/Qualifications
There is no recognized certification program for persons who
perform methacholine challenge testing. The pulmonary laboratory director is responsible for evaluating and/or verifying
the training and qualification of the person(s) who perform thetest. At a minimum, the technician should:
1. Be familiar with this guideline and knowledgeable about
specific test procedures
2. Be capable of managing the equipment including set-up,
verification of proper function, maintenance, and cleaning
3. Be proficient at spirometry
4. Know the contraindications to MCT
5. Be familiar with safety and emergency procedures
6. Know when to stop further testing
7. Be proficient in the administration of inhaled bronchodilators and evaluation of the response to them
Rationale. These requirements are standard testing elements designed to ensure good-quality results and patient
safety. It is estimated that about 4 d of hands-on training andat least 20 supervised tests are required for a new technician to
become proficient in methacholine challenge testing (36).
D. Safety
Inhaled methacholine causes bronchoconstriction. The safetyof both patients and technicians should be considered in thedesign of the test room and the testing procedures.
Precautions for patient safety. The medical director of thelaboratory, another physician, or another person appropriately trained to treat acute bronchospasm, including appropriate use of resuscitation equipment, must be close enough to
respond quickly to an emergency. Patients should not be left
unattended during the procedure once the administration of
methacholine has begun.
Medications to treat severe bronchospasm (30) must bepresent in the testing area. They include epinephrine and atropine for subcutaneous injection, and albuterol and ipratro-

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TABLE 2
FACTORS THAT DECREASE BRONCHIAL RESPONSIVENESS
FactorMedications
Short-acting inhaled bronchodilators, such as isoproterenol,
isoetharine, metaproterenol, albuterol, or terbutaline
Medium-acting bronchodilators such as ipratropium
Long-acting inhaled bronchodilators, such as salmeterol,
formoterol, tiotropium
Oral bronchodilators
Liquid theophylline
Intermediate-acting theophyllines
Long-acting theophyllines
Standard pz-agonist tablets
Long-acting pz-agonist tablets
Cromolyn sodium
Nedocromil
Hydroxazine, cetirizine
Leukotriene modifiers
Foods
Coffee, tea, cola drinks, chocolate

Minimum Time Intervalfrom Last Dose to Study

Ref. No.

8h

45,46

24 h
48 h
(perhaps 1 wk for tiotropium)

20,47
48,49
so,51

12h
24 h
48 h
12h
24 h
8h
48 h
3d
24 h
Day of study

52

Note: The authors do not recommend routinely withholding oral or inhaled corticosteroids, but their antiinflammatory effect may decrease bronchial responsiveness (53, 54). Inhaled corticosteroids may need to be withheld depending on the question being asked.

3. Testing.
a. Subjects must be able to understand the procedure and perform reliable spirometric maneuvers.
b. Subjects should be seated comfortably throughout the test.
c. A brief physical examination of the chest and lungs may be
useful but is not required.
Rationale. The pretest evaluation will alert the technician
to important issues, including (1) the presence of contraindications to proceeding with the test; (2) conditions or exposures,such as a recent viral infection, that could temporarily increase
airway responsiveness (58, 62-64) and cause a false-positive
response; (3) the presence of medications that may alter airway responsiveness. Influenza vaccination, the menstrual cycle, antihistamines, and oral contraceptives do not significantly
affect airway responsiveness (65-67). A number of medications, most notably anticholinergic and P-agonist inhalers, cantemporarily reduce airway responsiveness, potentially causing
a false-negative response (20,23-25,46,52).
F. Choice and Preparation of Methacholine

Methacholine (acetyl-P-methylcholine chloride), available asa dry crystalline powder, is the agent of choice for nonspecificbronchoprovocation challenge testing. Food and Drug Administration (FDA)-approved methacholine (Provocholine) is

TABLE 3
FACTORS THAT INCREASE BRONCHIAL RESPONSIVENESS
FactorDuration of Effect

Ref. No.

Exposure to environmental antigens
Occupational sensitizers
Respiratory infection
Air pollutants
Cigarette smoke
Chemical irritants

l-3 wkMonths
3-6 wk1 wkUncertain*
Days to months

25
55,56
57,58
59
60
61

*Studies of the acute effects of smoking on airway hyperreactivity and methacholine
challenge testing are not consistent (60). There is some evidence of a brief acute effectthat can be avoided by asking subjects to refrain from smoking for a few hours before
testing.

available in prepackaged, sealed lOO-mg vials. Industrial sourcesof methacholine appear to work as well as Provocholine (68).
The advantages of FDA-approved methacholine are that it isapproved for human use and is required to meet good manufacturing practices for quality, purity, and consistency. The bromide salt of methacholine may be substituted for the chloride
salt, although it is not currently available in an FDA-approved
form. Methacholine powder is very hygroscopic. Bulk powder
should be stored with a desiccator in a freezer. Sealed prepackaged vials do not require desiccation or freezing. Sterile
normal saline (0.9% sodium chloride) with or without 0.4%
phenol may be used as the diluent. The committee prefers theuse of normal saline without phenol. Phenol-containing salineis specified for the dilution of Provocholine. There is no evidence that adding a preservative such as phenol to sterile saline diluent is necessary (69) nor is there evidence that use ofphenol adversely affects MCT. Both diluents are widely used.
The potential benefit of adding phenol is reducing the potential for bacterial contamination. The pH of methacholine innormal saline solution is weakly to moderately acidic depending on the concentration of methacholine. Buffered solutions
are less stable and should not be used as the diluent (69-71).
Methacholine solutions should be mixed by a pharmacist orother well-trained individual using sterile technique. The vials
should be labeled as methacholine with the concentration andan expiration date and stored in a refrigerator at about 4” C.
When prepared with saline diluent and stored at 4” C, methacholine solutions of 0.125 mg/ml and greater should be stablefor 3 mo (69, 71, 72). The package insert for Provocholine
specifies the use of normal saline containing 0.4% phenol as
the diluent and recommends the solution not be stored longer
than 2 wk and that the 0.025mg/ml solution be mixed on the
day of testing. We are not aware of published information on
the stability of methacholine in normal saline with phenol solution; such studies are needed. In the absence of this information, we recommend that the package insert recommendations
for Provocholine storage be followed when methacholine ismixed with saline containing phenol. Solutions of methacholine should be warmed to room temperature before testing begins. Any unused methacholine solution remaining in a nebulizer should be discarded.

American Thoracic Society

Rationale. Choice of agent. Methacholine and histamine
produce bronchoconstriction at nearly equivalent concentrations (73,74). Methacholine is currently more commonly used(29) and is preferred to histamine because histamine is associated with more systemic side effects, including headache,
flushing, and hoarseness. In addition, BHR measurements may
be less reproducible when using histamine (75-77).
Methacholine is a synthetic derivative of the neurotransmitter acetylcholine, a substance that occurs naturally in the
body. Methacholine is metabolized more slowly by cholinesterase; its effects can be blocked or lessened by atropine orsimilar anticholinergic agents.
Conditions. Acidic methacholine solutions with concentrations greater than 0.3 mglml (pH < 6) remain stable for at least
3 mo when stored at 4” C (69,71,72,78). One committee member’s experience is that concentrations of 0.125 mg/ml are clinically stable for 3 mo, but this observation has not been documented in the literature and a conservative approach should betaken until more information is available on the stability oflower concentrations. Methacholine is rapidly decomposed byhydrolysis as the solution pH increases above six (71). Lower
concentrations of methacholine lose potency faster when stored
at room temperature because they are less acidic than higher
concentrations (71, 72). The concentration of methacholine
will change during nebulization if cold solutions are not allowed
time to warm to room temperature before use (79). Solution
remaining in a nebulizer after it has been used will concentrateby evaporation and should not be reused.
Preparing solutions. Accurate sterile mixing is very important for the accuracy of the test results and for the safety of patients. Only trained individuals should mix and label methacholine solutions.
C. Dosing Protocols
Many different dosing protocols have been used. Each has advantages and disadvantages and the committee was unable tocome to a single recommendation. We were able to narrow
the choices to two: (I) the 2-min tidal breathing method and(2) the five-breath dosimeter method. The FDA approval for
the Methapharm (Brantford, ON, Canada) methacholine(Provocholine) is based on the five-breath technique and adosing schedule using methacholine concentrations of 0.025,
0.25, 2.5, 10, and 25 mg/ml. A dilution scheme provided intheir product information is designed to accurately produce
these concentrations. The concentrations in the Provocholine
product information can be used in the five-breath dosimeter
method, although the committee prefers the dosing schedule
described below because the dosing steps are even and because of concerns about the safety of the lo-fold changes in dilution strength in the Provocholine protocol. Dilution schemes
for the two recommended dosing schedules, based on a lOOmg vial of Provocholine, are presented in Table 4.
Rationale. Four common methods of aerosol generationand inhalation are used (1): (I) dosing during a deep inhalation, using a Y tube occluded by the thumb; (2) five breaths ofa fixed duration, using a dosimeter at the beginning of a deep
inhalation (5, 80,81); (3) a hand bulb nebulizer activated during inhalation (82); and (4) continuous nebulization while tidal
breathing for 2 min (4, 83). All of these methods give similar
results (74, 81, 84-88). The two techniques recommended inthis statement are those most widely used in North America
and Europe. The hand bulb nebulizer (Yan protocol) is infrequently used in the United States (3) and has poorer reproducibility when used with patients who have not previously
performed methacholine challenge tests (87). It is widely used
for epidemiological surveys.

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1. Two-minute tidal breathing dosing protocol. The 2-min
tidal breathing method is, with some variation, based on the
protocol recommended by the Canadian Thoracic Society (4,89). Refer to the flow chart in Figure 2. Details on spirometry
technique are found in the section, Spirometry and Other Endpoint Measures.
a. Prepare the following 10 doubling concentrations of methacholine in sterile vials, place them in a holder, and store
them in a refrigerator:
Diluent: 0.03 0.06 0.125 0.25 0.50 1 2 4 8 16
mg/ml (see Table 4)
The use of the diluent step is optional. An optional shortened dosing regimen can be used under certain circumstances (see Rationale).
b. Remove the vials from the refrigerator 30 min before testing, so that the mixture warms to room temperature before
use. Insert 3 ml of the first (diluent or lowest) concentration into the nebulizer, using a sterile syringe.
C. Perform baseline spirometry and calculate a target FEV,
that indicates a 20% fall in FEV, (baseline [or diluent]
FEV, x 0.8).
d. Use a nebulizer setup such as shown in Figure 1. Use drycompressed air to power the nebulizer, and set the pressure
regulator to 50 lb/in2. Flow meter accuracy should bechecked with a rotameter (Matheson Tri-Gas, Montgomeryville, PA). Adjust the flow meter to deliver the output established during the calibration procedure (0.13 ml/min,+- 10%). Attach a new exhalation filter (optional).
e. Instruct the patient to relax and breathe quietly (tidal breathing) for 2 min. Apply a noseclip. Set the timer for 2 min.
f. Ask the patient to hold the nebulizer upright, with themouthpiece in his/her mouth. A face mask with a noseclip
is a valid alternative and may be easier for some subjects(90). Start the timer and begin nebulization.
g. Watch the patient to ensure that he/she is breathing comfortably and quietly, and not tipping the nebulizer. After

TABLE 4
DILUTION SCHEMES FOR THE TWO RECOMMENDEDMETHACHOLINE DOSING SCHEDULES
Label Strength

Take

Add NaCl (0.9%)

Obtain Dilution

A. Dilution schedule* using 100.mg vial of methacholine chloride and the 2-min
tidal breathing protocol
100 m g

100 m g
3 m l of dilution A
3 ml of dilution B
3 m l of dilution C
3 m l of dilution D
3 ml of dilution E
3 m l of dilution F
3 m l of dilution C
3 ml of dilution H
3 m l of dilution I

6.25 ml
3 ml
3 ml
3 ml
3 ml
3 ml
3 ml
3 ml
3 ml
3 ml

A: 16 mg/ml
B: 8 mg/ml
C: 4 mg/ml
D: 2 mglml
E: 1 mg/ml
F: 0.5 mg/ml
C: 0.25 mg/ml
H: 0.125 mg/ml
I: 0.0625 mg/ml
J: 0.031 mg/ml

B. Optional dilution schedule using lOO-mg vial of methacholine chloride andfive-breath dosimeter protocol
100 m gl

100 mg
3 ml of dilution A
3 ml of dilution B
3 ml of dilution C
3 ml of dilution D

6.25 ml
9 ml
9 ml
9 ml
9 ml

Schedule obtained from Methapharm (Brantford, ON, Canada).

A: 16 mg/ml
B: 4 mg/ml
C: 1 mg/ml
D: 0.25 mg/ml
E: 0.0625 mg/ml

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2. Five-breath dosimeterprotocol. The five-breath dosimeter
protocol was first standardized by the National Institutes of
Health (NIH) Institute of Allergic and Infectious Diseases in1975 (5) and is presented as an alternative method by the European Respiratory Society (1). It is widely used in researchstudies. We have modified it by recommending quadrupling
doses rather than doubling doses. The Provocholine dosing
schedule is also acceptable. Refer to the flow chart in Figure 2.
a. Set up and check the dosimeter.
b. Prepare the following five concentrations of methacholine
in sterile vials; place them in a holder; and store them in arefrigerator. (Note: in contrast to the 2 min tidal breathing
method, only every other concentration is used, resulting inincrements of quadrupling doses.) Use of a 32 mg/mL concentration is optional; it would primarily be used for research and epidemiological studies.
Diluent: 0.0625 0.25 1 4 16 mg/ml (see Table 4)

Admmrster next dose of methachohne.
and perform sp~omctry after the approprwe delay

Use of the diluent step is optional.
Remove the vials from the refrigerator 30 min before testing, so that the contents warm to room temperature before
use. Insert 2.0 ml of the first concentraGon into the nebulizer,
using a sterile syringe. (Some nebulizer models may require
more than 2.0 ml of solution for reliable aerosolization.)d. The patient is seated throughout the test.
Perform baseline spirometry.
;. Briefly open the dosimeter solenoid to make sure the nebulizer is nebulizing.
g. Ask the patient to hold the nebulizer upright with the mouthpiece in his/her mouth. Watch the patient during the breathing maneuvers to ensure that the inhalation and breathhold
are correct and that the nebulizer is not tipped. The patient
should wear a noseclip while inhaling from the nebulizer.
h. At end exhalation during tidal breathing (functional residual capacity), instruct the patient to inhale slowly anddeeply from the nebulizer. Trigger the dosimeter soon after
the inhalation begins; dosimeters may do this automatically. Encourage the patient to continue inhaling slowly(about 5 s to complete the inhalation) and to hold thebreath (at total lung capacity, TLC) for another 5 s.
1. Repeat step h for a total of five inspiratory capacity inhalations. Take no more than a total of 2 min to perform these
five inhalations.
.i. Measure the FEV, at about 30 and 90 s after the fifth inhalation from the nebulizer. Obtain an acceptable-quality
FEV, at each time point. This may require repeated attempts. Perform no more than three or four maneuvers after each dose. It should take no more than 3 min to perform these maneuvers. To keep the cumulative effect of
methacholine relatively constant, the time interval between
the commencement of two subsequent concentrations
should be kept to 5 min.
k. At each dose, report the highest FEV, from acceptable maneuvers.
1. If the FEV, falls less than 20%, empty the nebulizer, shakeit dry, and trigger the dosimeter once to dry the nebulizer
nozzle. Add 2.0 ml of the next higher concentration, andrepeat steps g-j.
m. If the FEV, falls more than 20% from baseline (or the highest concentration has been given), give no further methacholine, note signs and symptoms, administer inhaled albuterol, wait 10 min, and repeat the spirometry. If vocal
cord dysfunction is suspected and the patient’s symptoms
allow it, full inspiratory and expiratory flow volume loops
may be performed before giving the bronchodilator.
C.

figure 2. Methacholine challenge testing sequence (flow chart).
*The choice of the FEV, value considered a contraindication mayvary from 60 to 70% of predicted. **The final dose may vary depending on the dosing schedule used. Final doses discussed in thisstatement are 16, 25, and 32 mg/ml.

exactly 2 min, turn off the flow meter and take the nebu-

lizer from the patient.
h. Measure the FEV, about 30 and 90 s after the nebulizationis completed. Obtain an acceptable-quality FEV, at each time
point. This may require repeated attempts. Perform no morethan three or four maneuvers after each dose. It shouldtake no more than 3 min to perform these maneuvers. To
keep the cumulative effect of methacholine relatively constant, the time interval between the commencement of two
subsequent concentrations should be kept to 5 min.
i. At each dose, report the highest FEV, from the acceptablemaneuvers.
j. If the FEV, falls less than 20%, empty the nebulizer, add 3 mlof the next highest concentration, and repeat steps e-h above.
k. If the FEV, falls more than 20% from baseline (or the highest concentration has been given), give no further methacholine, note signs and symptoms, administer inhaled albuterol, wait 10 min, and repeat the spirometry. If vocal
cord dysfunction is suspected and the patient’s symptoms
allow it, full inspiratory and expiratory flow volume loops
may be performed before giving the bronchodilator.

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American Thoracic Society

3. Rationale. Dosing schedules. Many different dosing protocols have been used by investigators and laboratories. Doubling concentrations are widely recommended for research
protocols and are mathematically attractive but the smaller
steps increase the time needed for a test. As a compromise, forclinical testing, we recommended quadrupling increments forclinical testing with the five-breath dosimeter method. Fewer
concentrations have been used by many investigators in orderto save time (41,91-9.5) without any apparent increase in riskof severe bronchospasm. If MCT is used to determine changes
in airway reactivity after therapy in patients known to haveasthma, using doubling doses will give more precise PCZo (provocative concentration causing a 20% fall in FEV,) values.
Optional shortening of the tidal breathing protocol. The
2-min tidal breathing protocol may be shortened (dependingon the clinical situation) by adjusting the starting concentration (4). For example, in a diagnostic test for a subject not
known to have asthma, taking no asthma medications, withnormal lung function, and no response to diluent, a starting
dose of 1 mg/ml is quite safe. In addition, when the FEV, has
fallen less than 5% in response to a dose of methacholine, thenext concentration may be omitted; a fourfold increase in dosage is quite safe under these circumstances. Caution: Smallchildren with asthma symptoms are more likely than adults tohave severe airway hyperresponsiveness and more caution inincreasing the concentration at each step is warranted. Thisapparent increased sensitivity in children may reflect an increased dose per unit weight (96).
Test techniques. The speed at which methacholine is inhaled affects how it is deposited and, consequently, affects test
results. Rapid inhalation flow (> I L/s), instead of the recommended slow inhalation over 5 s, will reduce measured PC& inmany patients (97,98). Nose clips are used to prevent dilutionof the inhaled solution with air through the nose during theslow inhalations. The nebulizer is held upright because tipping
may reduce or stop aerosol generation as the fluid intake nozzle moves above the fluid line. In addition, the output of somenebulizer models may depend on a vertical position. Inhalation of the aerosol via face mask (with the nose occluded) gave
equivalent results compared with using a mouthpiece (90).
FEV,: Timing and selection of values for interpretation.

The timing of FEV, measurements at 30 and 90 s after the inhalation is based on considerable experience with measurements at these times. Recommendations for interpretation arelargely based on measurements performed according to thistiming schedule and use of the largest acceptable FEV, as theoutcome variable is widely accepted. Some investigators prefer to report the lowest FEV,, reasoning this will avoid the effect of an increase in FEV, as the methacholine wears off (99).
However, this approach assumes the technician will be able toensure high-quality tests and discard all unacceptable maneuvers before selecting the lowest FEV,. If all FEV, maneuvers
are completed in the recommended time (< 3 min) it is highly
unlikely that the effect of methacholine will wear off.
Use of a diluent step. The opinions of the committee members regarding the desirability of starting with a diluent (control) were divided; most current protocols start with a diluent
step. An advantage of starting with a diluent is that it gives patients an opportunity to learn the technique of inhaling fromthe nebulizer and practice in performing spirometry. In addition, most reference data used for interpretation are based onstudies that used a diluent step and use of a diluent step provides a better link to interpretative data by ensuring technicalcomparability. Other committee members felt the rationale
for using a diluent was weak. They argued: the lowest concentration of methacholine was chosen so that only the most hy-

perresponsive patient with asthma will respond and the use ofa diluent control does not improve the safety of the test. The
PCZO is not affected by starting with a diluent (100). The addition of a diluent control adds 5 min to each test. Only 1% of
patients tested using a diluent (control) respond to the diluent
with a 20% or greater fall in FEV, (101) and the clinical meaning of a positive response to the diluent is unknown. Suchpatients may be experiencing FVC maneuver-induced bronchospasm, but this should have been detected before the methacholine study was scheduled.
When a diluent step is used, the postdiluent FEV, is thereference point for comparison. We recommend a 20% fall in
FEV, following diluent as the threshold of significance forconsistency with the thresholds used in the rest of the test. Although some investigators have used a 10% fall in FEV, as thethreshold to determine a positive response to the diluent, thisthreshold is close to the 95th percentile confidence interval of
FEV, repeatability in patients with BHR and increases the
chance of a test failure.
Ii. Nebulizers and Dosimeters

Nebulizers for the tidal breathing method. The nebulizer mustdeliver an aerosol with a particle mass median diameter(MMD) between 1.0 and 3.6 p,rn [e.g., the English Wright nebulizer (Roxon Medi-Tech, Montreal, PQ, Canada) (4) generates particles between 1.0 and 1.5 MMD and is generally used
for this method]. It is acceptable to perform this techniquewith other brands of nebulizers with similar characteristics.
For other nebulizer brands, reviews of nebulizer performance
may be useful in making initial selections (102, 103); further
validation of nebulizer performance is recommended. Avoid
the use of nebulizers with MMD less than 1.0 pm. Flow must
be adjusted for each nebulizer to obtain an output within 10%
of 0.13 ml/min. Variation of MMD between 1.3 and 3.6 pm
does not influence measurement of airway responsiveness whenusing the 2-min tidal breathing method (104). It is not, therefore, necessary to check the particle size generated by each individual nebulizer once the MMD range for a nebulizer model
has been found to be between 1 .O and 3.0 pm.
To measure nebulizer output for the tidal breathing method,
perform the following steps:
1. Put 3 ml of room temperature saline into the nebulizer.
2. Weight the nebulizer, using a balance accurate to 1.0 mg(preweight).
3. Adjust the flow meter to 7.0 L/min and nebulize for exactly
2 min.
4. Reweigh the nebulizer (postweight). Empty the nebulizer.
5. Repeat steps 14 three times for each of the following air
flows: 7.0, 8.0, and 9.0 Umin (or 4.0, 5.0, and 6.0 L/min forsome nebulizer models).
6. Calculate and plot the average nebulizer output at each airflow.
a. The nebulizer output in milliliters per minute, assuming
1 ml of saline equals 1,000 mg, is calculated as
Output (mUmin) = [ (preweight (mg) postweight (mg))/time (min)]/ 1,000.

(1)b. By interpolation, determine the airflow that will generate an output of 0.26 ml over 2 min (0.13 mUmin). Record
the airflow for the nebulizer and the date of the calibration check.
7. Subsequent checks of nebulizer output need only test the
nebulizer output at the flow that generates the correct output. If the output is within specification (0.13 ml/min,
2 10%) testing at other flows is not necessary. Alternative

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techniques for nebulizer calibration checks have been described that may be more accurate and that are applicable
to respiratory function laboratories (105).
Nebulizers for the five-breath dosirneter method. Nebulizers
for the five-breath method should deliver 9 ~1 (0.009 ml) ?
10% of solution per 0.6-s actuation during inhalation (104).
The DeVilbiss (Somerset, PA) model 646 nebulizer is commonly used for this technique (Figure 1). Other nebulizers
with equivalent characteristics and output are acceptable. Because the DeVilbiss 646 model has high between-unit output
variability (106, 107) each nebulizer must be adjusted and its
output checked before it is put into service. The extra vent on
the DeVilbiss 646 nebulizer must be closed during methacholine challenge testing, as the nebulizer output increases and isvariable when air can be entrained into the nebulizer (108). A
flow regulator may be added to the nebulizer to control therate of inspiratory flow. If used, the flow regulator must be included in the system during calibration. Nebulizer output is influenced by the gap between the jet orifice and the tip of thecapillary tube (Figure 1). The position of the impinger arm
also influences the output of the nebulizer but the effect varies
from nebulizer to nebulizer, so no single position can be recommended (107). In the Lung Health Study, the impinger arm
was placed so that its large curve pointed toward the mouthpiece when the nebulizer was assembled. A jet orifice-capillary tube gap of 0.01 in. (0.254 mm), measured with a spark
plug tool, was used (P. Enright, personal communication).
These are reasonable starting places. Once the nebulizer output is satisfactory, the impinger arm should be carefully glued
in the position used during calibration. An exhalation filter
may be added to the nebulizer cap opposite the mouthpiece(Figure 1). A single nebulizer may be used for all concentrations, provided it is emptied and the nozzle dried between
doses. Alternatively, six or seven separate calibrated nebulizers may be filled before the test. If separate nebulizers areused, they must be carefully labeled to avoid dosing errors.
For the five-breath dosimeter technique, outputs are checkedby weighing the nebulizer containing 2 ml (or the volume used
for testing) of room temperature, sterile normal saline before
and after 10 actuations with a technician simulating the test byinhaling slowly from the nebulizer. The scale used must be accurate to at least 0.5 mg. For the DeVilbiss 646 nebulizer, thetarget output is 90 p_l + 10% (0.09 ml [90 mg] + 10%) for the
10 actuations.
Monitoring nebulizer performance. Nebulizer output varies
from model to model and from unit to unit and may vary withtime depending on how the nebulizer is maintained and cleaned(109). The actual output of each nebulizer used must be measured initially and at regular intervals. Because nebulizer performance over time may vary depending on individual laboratory
use, maintenance, and cleaning practices, each laboratory should
establish its own nebulizer monitoring schedule. We recommendthat each laboratory check output after every 20 uses until an appropriate testing schedule is established for the laboratory.
The dosimeter. The dosimeter is an electrically valved system that enables the technician to administer aerosol for 0.6 s
during inhalation from the nebulizer. The dose may be triggered manually by pressing a button or by an automatic system that delivers a single dose soon after the onset of a deep
breath. Useful dosimeter options include a dose counter display (to remind the technician how many doses have been
given), a feedback tone slowly increasing in frequency for 5 s
after the dose is delivered, followed by a steady tone lastingfor 5 s (to encourage a slow inhalation and breath holding at
TLC), and a 5-min timer.

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Dosimeter systems should be set up and checked according
to the manufacturer recommendations. Manufacturers should
give explicit instructions for (1) dosimeter and nebulizer setup
and use to deliver the recommended methacholine concentrations and (2) operational checks to ensure proper ongoing
function of the system.
The committee divided on the need for a dosimeter. Dosimeters may improve the accuracy and repeatability of thedose delivered to the airways but add additional expense.
They are widely used in both clinical and research challenge
testing. Automatic triggering of the dosimeter during the onset of inhalation is an attractive feature but manual triggering
is acceptable. At least one researcher (110) has reported thatexact timing of the dose did not affect the methacholine response, an argument against the need for automatic triggering.
Further studies are needed to resolve this issue. It is importantto simulate an actual test when nebulizers are calibrated because nebulizer output may be less if the dosimeter is activated without the inhalation.
Rationale. Nebulizers. Commercially available nebulizers
used to deliver bronchodilator drugs have a wide range ofcharacteristics. Early investigators used DeVilbiss 40 glass
nebulizers. DeVilbiss 646 nebulizers have also been used bymany investigators performing inhalation challenges. Theiroutput characteristics have been well described ( 111, 112) andthey are relatively inexpensive. Inexpensive plastic nebulizers
are generally not manufactured with tight output tolerances
and their volume output should be checked before use (107,113,114).
The output of a DeVilbiss 646 nebulizer varies 2:l with theextra vent open or closed. It should be permanently closed(115) for methacholine challenge use, as the output is increased by inhaling through the nebulizer and also varies overtime and after disassembly and reassembly of the baffle (109,and personal communications from Robert Wise and Paul Enright). At least 1 ml of solution should remain at the end of
nebulization, because output decreases below this level. A
2 10% range in nebulizer output is considered acceptablewith doubling or quadrupling concentration increments. Nebulizer output is also directly proportional to the airflow driving the nebulizer (115).

Effect of nebulizer and technique differences on test outcomes. The two proposed techniques appear to give similar re-sults in both children (116) and adults despite the substantial
differences in administration technique and equipment. The
Wright nebulizer used for the 2-minute tidal breathing has avery small particle size distribution with close to 80% of theoutput in the respirable fraction (RF). The RF is defined as
the fraction of aerosol contained in droplets of < 5 pm, which,
if inhaled via a mouthpiece, would have a high probability ofdeposition below the vocal cords (117, 118). For a calibrated
output of 0.13 ml/min and a respiratory duty cycle (inspiratory
time divided by total respiratory cycle time, Tt/Ttot) of 0.43,
for 2 min of tidal breathing, approximately 0.089 ml of methacholine solution would be delivered below the cords (119).
While much of this would be deposited, many smaller particles
will be exhaled.
For the five-breath method, a DeVilbiss 646 nebulizer isused with an output of 9 pl(O.009 ml) per 0.6-s activation for a
total delivery of 0.045 ml (104). Approximately 70% of the total delivery would be within the RF (107) for an estimatedtotal dose of 0.032 ml delivered below the cords. It would appear, therefore, that the tidal breathing method should cause
bronchoconstriction at a lower concentration of methacholine.
The reasons such differences are not apparent include the following: (I) methacholine is rapidly metabolized. The tidal

American Thoracic Society

breathing method ensures that there will be at least 2.5 min between the start of the inhalation and the first FEV,, while thefive-breath technique moves more quickly with less time forthe effect of methacholine to wear off; (2) many of the small
particles from the Wright nebulizer may either be exhaled ordeposited in the alveoli, where they cannot cause bronchoconstriction; (3) the logarithmic increase in dose would makesmall differences in airway deposition very difficult to detect;and (4) the repeated deep inhalations in the five-breath technique may affect airway caliber (see Section I, Rationale).
By chance rather than by design, the two methods appear
to yield very similar results. Because the inspiratory flow of
the subject will greatly exceed the driving flow to the nebulizer, the parameters that will influence deposition will be TI/
Ttot for the tidal breathing method and the total duration of
inspiration for the five-breath technique, neither of which issize dependent. This means that the expected deposition willbe the same but the deposition per unit weight (or lung size)
will be greater in smaller subjects than larger ones. This increased dose per unit size may be one of the factors that explains the apparent increased sensitivity in small children (96).
I. Spirometry and Other End-point Measures
Spirometry. Change in FEV, is the primary outcome measure

for MCT. Spirometry should meet ATS guidelines (120). Special care should be taken to obtain high-quality baseline FEV,
measurements because unacceptable maneuvers may result infalse-positive or false-negative results. The quality of the flowvolume curves should be examined after each maneuver. Full
FVC efforts lasting at least 6 s should be performed at baseline (and after diluent, if applicable). If FEV, is the only outcome being measured, the expiratory maneuver can be shortened to about 2 s. If a shortened expiratory time is used,technicians should take care that the inspiration is complete
because incomplete inhalations will result in a false reductionin FEV, and abbreviated flow-volume tracings may not show
an inadequate inhalation. If other spirometric outcome variables are used or if vocal cord dysfunction is suspected, full
FVC maneuvers should be performed throughout the test.
The highest FEV, value from acceptable tests is selected forthe outcome variable after each dose.
The quality of the maneuvers contributes to the confidencewith which an interpretation can be made. The following
scheme of quality control (QC) grades reported (printed) after each level of methacholine may be used to assist the interpreter.
A = two acceptable FEV, values that match within 0.10 L
B = two acceptable FEV, values that match within 0.20 L
C = two acceptable FEV, values that do not match within
0.20 L
D = only one acceptable FEV, maneuver
F = no acceptable FEV, maneuvers
All acceptable quality tests performed at 30 and 90 s after
each dose of methacholine are used to calculate repeatability.
Bear in mind that the repeatability criteria are based on traditional spirometric measurements and may not apply directly
to tests performed after the administration of methacholine.
Failure to meet repeatability standards should be used only toassist interpretation and not to exclude data from analysis.
Studies are needed to better define FEV, repeatability criteria
for methacholine challenge tests.
Forced inspiratory maneuvers. If vocal cord dysfunction issuspected, or if inspiratory stridor is noted during the baseline
examination or after the final dose of methacholine, perform
at least three full spirograms that include forced inspiratory

317

vital capacity (FIVC) maneuvers. Vocal cord dysfunction (VCD)
may be revealed as spontaneous or MCT-induced limitationof forced inspiratory flow resulting in a plateau in flow on the
FIVC curves (121-124). Patients with vocal cord dysfunction
or central airway obstruction are not common, but often havea history suggesting asthma and may be referred for bronchoprovocation testing when the diagnosis of asthma is either
considered or questioned.
Body plethysmography. Measures of airway resistance(Raw), usually expressed as specific conductance (sGaw), arealternative end points for MCT but should be used primarily inpatients who cannot perform acceptable spirometry maneuvers(125,126). In patients with asthma and COPD, changes in Raw
usually parallel changes in FEV, with MCT (127-l 29), but both
Raw and sGaw are more variable than FEV,. A larger percent
change (e.g., 45%) is therefore required for a positive test. It is
not necessary to measure total lung capacity (TLC) during
MCT, because TLC usually does not change (13s-132). A decrease in vital capacity reflects an increase in residual volume.
Transcutaneous oxygen. Measurements of transcutaneous
oxygen tension (PtcoZ) correlated well with measurements oflung function in children (133-137). Ptcoz may be a useful end
point in infants, young children, and adults (138) whose cooperation cannot be obtained for spirometry. Use of Ptco, should
be restricted to laboratories with experience in its use as an
MCT end point.
Forced oscillation. Forced oscillation or impulse techniques
and occlusion or interrupter techniques have recently been assessed (136,137). These approaches do not require patient effort and may be useful in testing patients who cannot perform
acceptable spirometry maneuvers. At this time, their use should
be reserved for patients who cannot perform acceptable spirometry maneuvers and should be restricted to laboratories
with expertise in their application and interpretation.
Rationale. The bronchial smooth muscle stimulation induced by methacholine inhalation results in airway narrowing
and airway closure. In healthy persons and patients with mild
asthma, the deep inhalation that precedes an FVC maneuver
causes transient bronchodilation that may last for up to 6 min(139-141). In patients with more severe asthma, this response isblunted or absent and the maneuver may result in bronchoconstriction (132, 141-143). In patients being clinically tested for adiagnosis of asthma, this difference in the effect of deep inhalations on airways may contribute to the better ability of FEV,, incomparison with measurements of Raw or sGaw, to separate
patients without asthma from patients with asthma (127, 144).
However, because most diagnostic challenge tests are performed on individuals who are either nonasthmatic or mildly
asthmatic, both are likely to have the bronchodilator response.
Changes in peak expiratory flow (PEF) often parallel changes
in FEV, during bronchoconstriction but have the disadvantagesof being (2) more effort dependent and less reproducible and(2) less sensitive in detecting bronchoconstriction (145-148).
Although not commonly used as an end point, change in FVC isreported to correlate with disease severity (149).
Changes in airway resistance may be more sensitive thanchanges in FEV, for detecting bronchoconstriction, but FEV,
is superior to other parameters for discriminating relatively
healthy persons from those with asthma (127,144). Other end
points such as transcutaneous oxygen and forced oscillation
have promise but are still experimental and are not recommended for routine clinical testing at this time.
J. Data Presentation
The results are reported as a percent decrease in FEV, frombaseline (or postdiluent if a diluent step is used). Data should

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be presented for each step in the protocol, including the postbronchodilator test. At a minimum, all of the elements in thesample bronchoconstriction report in A PPENDIX C should be
included, including volume-time or flow-volume curves. A
single number, PC& (with one decimal place), may be used tosummarize the results for clinical purposes. Unless stated otherwise, it may be assumed that the PC& is calculated from thechange in FEV,.
If the FEV, does not fall by at least 20% after the highest
concentration (e.g., 16 mg/ml) then the PC,,, should be reported as “> 16 mg/ml.” Do not extrapolate beyond the final
concentration. If the FEV, falls by more than 20% after inhalation of the diluent, a P(& is not reported. Instead, state“there was a significant decrease in lung function after inhalation of the diluent and methacholine was not given.”
For manual graphic calculation of PC&, the change in
FEV, as a percentage of the reference value may be plottedon the ordinate against the log concentration on the abscissa.
The following equation can be used to calculate the interpolated PC&, (1,4,150):

PC *tj = antilog log C, +(logC2-logC,)(20-Rr)
R2-RI

1 (2)

where
C, = second-to-last methacholine concentration (concentration preceding C,).
CZ = final concentration of methacholine (concentration
resulting in a 20% or greater fall in FEV,)
R, = percent fall in FEV, after Ci
R2 = percent fall in FEV, after C2
Rationale. Exponential models are better than linear models for interpolating between concentrations or doses (150,
151). The provocative concentration that results in a 20% fallin FEV, (PC,,,) was selected as the outcome variable because
it is simple to calculate and avoids the complicated and controversial aspects of estimating a provocative dose (PD,).

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Sensitivity and specificity of methacholine challenge tests
Repeatability of methacholine challenge test
A general scheme for categorizing airway responsivenessusing PC&, for use when the patient has no baseline airway obstruction, is shown in Table 5. The relationship between levelsof airway responsiveness and asthma are discussed below.
Relating the degree of airway responsiveness to questions
about individual patients. Using the degree of airway respon-

siveness to answer questions about individual patients assumes the test is properly performed, that no modifiers thatwould artificially alter airway responsiveness were present,
and that the patient’s prior probability of having current asthma
can be reasonably estimated. If the prior probability of asthma
is 30-70% and the PC& is > 16 mg/ml it may be stated with ahigh degree of confidence that the patient does not currently
have asthma (Figure 3) (152, 153). If the same patient has aPC&, < 1.0 mg/ml, the test provides strong confirmation of theclinical diagnosis of asthma. When the PC& is between 1 and
16 mg/ml, one must be more cautious about stating whether or
not the patient has asthma. It has been suggested that when
the PG, is low and the “asthma-like” symptoms induced by
MCT are similar to those previously reported by the patient,confidence is a diagnosis of asthma increases. This is intuitively attractive but we know of no published evidence supporting it.
In people with a PC& between 1 and 16 mg/ml and who
have no asthma symptoms (an unusual circumstance because
MCT would not be clinically indicated in such a setting) several possibilities exist: (1) there is mild intermittent asthma
but the patient is a “poor perceive? of asthma symptoms; (2)after exercise or inhalation challenges, the patient experiences
chest tightness that is perceived but not recognized as abnormal (154); (3) the patient never exercises or experiences environmental triggers of bronchospasm; (4) the mild BHR is due
to a cause other than asthma (postviral upper respiratory in-

K. Interpretation
The following factors should be taken into consideration wheninterpreting PC& results for an individual patient:
Pretest probability of asthma, including current asthma symptoms
Presence or degree of baseline airway obstruction
Quality of the patient’s spirometry maneuvers
Pretest questionnaire results (effects modifiers; see Tables 2
and 3)
Symptoms reported by the patient at the end-of-test
Degree of recovery after bronchodilator administration

TABLE 5
CATEGORIZATION OF BRONCHIAL RESPONSIVENESS
PC20
Ow/ml)

Interpretation*> 16
4.0-l 6
1.0-4.0< 1.0

Normal bronchial responsivenessBorderline BHR
Mild BHR (positive test)
Moderate to severe BHR

l Before applying this interpretation scheme, the following must be true: (I) baseline
airway obstruction is absent; (2) spirometry quality is good; (3) there is substantial
postchallenge FEV, recovery.

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1

pre-test probability
Figure 3. Curves illustrating pretest and posttest probability ofasthma after a methacholine challenge test with four PCZO values.
The curves represents a compilation of information from several
sources (10, 152, 153). They are approximations presented to illustrate the relationships and principles of decision analysis. They
are not intended to calculate precise posttest probabilities in patients.

American Thoracic Society
fection [URI], cigarette smoking, etc.); or (5) there is subclinical (asymptomatic) asthma that will become clinical asthma inthe future (155, 156). Between 1.5 and 45% of asymptomatic
persons with BHR may develop asthma during 2-3 yr of follow-up (157, 158).
In patients with a diagnosis of asthma, the correlation between degree of airway responsiveness and clinical severity ofasthma is significant, but not strong enough by itself to categorize the severity of asthma in individual patients (83,159-162).
Recent exposures causing airway inflammation or residual effects of antiinflammatory therapy (systemic or topical to the
airways) can easily change the degree of airway responsiveness so that the PCZo does not reflect the “usual” untreated severity of the patient’s asthma.
It is difficult to interpret the meaning of a low PC&, in a patient with baseline airway obstruction (163). For instance,
most patients with smoking-related COPD and mild to moderate baseline airway obstruction have BHR, but most haveno acute or chronic bronchodilator response or symptoms ofasthma (28, 128). It is even more difficult to interpret the significance of a change in PG,, when there has also been achange in baseline FEV, (which often occurs after successful
therapy).
Decision unalysis. The most common clinical indication for
MCT is to evaluate the likelihood of asthma in patients inwhom the diagnosis is suggested by current symptoms but is
not obvious. The continuous nature of airway responsivenessand the overlap in PC&, between the response of persons withhealthy lungs and patients who have unequivocal asthma requires decision analysis whether this is done formally or intuitively (1.52, 164-166).
The pretest probability (prior probability) is the likelihoodthat the patient has asthma before MCT results are considered. The posttest probability is the likelihood of asthma considering both the pretest probability and MCT results (posterior probability). The difference between the pre- and posttest
probabilities represents the contribution of MCT. The MCT
results can be helpful or misleading (1.52).
From an epidemiologic standpoint, the prior probability ofasthma for a given individual is equal to the prevalence ofasthma when a randomly selected population sample is being
tested and the subject’s medical history is not considered (e.g.,when methacholine testing is used to screen hundreds or thousands of military recruits or job applicants for asthma). The
prevalence of asthma is relatively low in the general population, usually about 5% (1.59, 167, 168), and the pretest probability in the example is also likely to be about 5%. In this example, an MCT test that is positive with a PC& of 1 mg/ml(using the curves in Figure 3) gives an estimated posttest likelihood of asthma of approximately 45%. Note that with pretest likelihoods in the S-15% range, the curves are steep andthe pretest likelihood is a very strong determinant of the posttest likelihood of asthma.
When a patient presents with symptoms suggestive of asthma,
the pretest probability is much higher than in the general population and is more difficult to define precisely. However,when the prior probability is between 30 and 70% MCT canbe quite useful. For example, with a P&, of 1 mg/ml, the posttest likelihood of asthma is roughly 90-98% with pretest likelihood estimates ranging from 20 to 80% (152; see Figure 3). If
the prior probability is 30% and the PCZo is 4 mg/ml, the posttest likelihood is about 70% (Figure 3). Optimal test characteristics (the highest combination of positive and negative predictive power) occurs when the pretest probability of asthma
is about 50% (10).

319
Categorical method of interpreting a methacholine challenge
test. The alternative “categorical” method for the clinical interpretation of methacholine challenge tests makes three assumptions: (I) MCT results are either positive or negative for
BHR; (2) asthma is either present or absent; and (3) there is a“gold standard” for diagnosing asthma. This popular method
ignores the continuous spectrum of airway responsiveness, thecontinuous nature of the degree of uncertainty in the diagnosis of asthma, and the lack of a gold standard for the diagnosis.
Using the categorical method, sensitivity is defined as thefraction (or percentage) of patients with the disease (asthma)
who have a positive test. Specificity is defined as the fractionof patients without asthma who have a negative test. A negative methacholine challenge result is commonly defined as nonresponse to the highest concentration (a PCZo > 8-25 mg/ml). A
positive test is often defined as a PCZo < 8 or < 16 mg/ml. The
optimal cutoff point (threshold) for separating a positive froma negative test is best accomplished using receiver-operator
characteristic (ROC) curves. When using ROC analysis, thebest PCZo cut point to separate patients with asthma fromthose without asthma is in the range of 8-16 mgiml (10, 169).
The false-positive rate for asthma is of concern when interpreting MCT results; in such cases the PG,, is < 8 mg/ml but
the patient does not actually have asthma. In testing general
population samples, patients with allergic rhinitis, and smokers with COPD, MCT has relatively high false-positive rates
and, therefore, poor positive predictive power (8, 169). About
30% of patients without asthma but with allergic rhinitis havea PC& in the borderline BHR range (144, 170-172). Our recommendation to use an intermediate area of “borderline
BHR” when the PCZo is between 4 and 16 mg/ml will improve
the specificity of MCT in comparison with previous studies. A
lower false-positive rate (with better test specificity) can beobtained by considering the pretest probability of asthma (using decision analysis).
A false-negative methacholine challenge result occurs when
the PCZo is greater than 8-25 mg/ml (no response to the highest concentration) in a patient who has asthma. This occurs
much less frequently than false-positive results. The negative
predictive power of MCT is more than 90% when the pretest
probability of asthma is in the range of 30-70% (153,172) andmost authors conclude that a negative MCT rules out asthma
with reasonable certainly in patients who have had asthma
symptoms during the previous 2 wk. Three factors should beconsidered before accepting a negative test as ruling out
asthma: (I) airway responsiveness may have been suppressed
if the patient was taking intensive antiinflammatory medications prior to the MCT. This issue may not be relevant if thepatient has current symptoms; (2) in patients without current
symptoms, the season for aeroallergen exposure may havepassed (173,174); and (3) a small fraction of workers with occupational asthma due to a single antigen or chemical sensitizer may respond only when challenged with the specificagent (175,176).
Effect of test repeatability on interpretation. Optimal repeatability of MCT results is most important when change in airway responsiveness is used in clinical research studies to measure outcome of asthma therapy in clinical research studies.
However, knowledge of short-term repeatability of the PC&, isalso useful when interpreting the results from the first MCT
performed by a single patient for clinical purposes.
Short-term within-subject repeatability studies (l-8 wk)
when patients are in a stable clinical state show that the 95%
confidence intervals for repeat determinations of methacholine PC2,, lie within 2 1.5 doubling doses (7.5, 81, 82, 87, 88,

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177-183). In other words, if the PC&, is measured as 4 mg/ml
during a baseline clinic visit, repeat MCT 2 wk later will give a
PC&, between 1.5 and 12 mg/ml in 95% of cases.
In addition to technical issues in standardization there are anumber of nontechnical or subject-related factors (which will
worsen or improve airway responsiveness) to be considered.
Such factors should either be controlled in order to maximize
repeatability, or recorded if they might explain changes in airway responsiveness. Factors that must be considered here include recent antigen exposure (which may have a considerable
influence on airway responsiveness), exposure to chemicalsensitizers (which may also have a large effect), recent respiratory tract infections (likely to have a relatively small effect),
variations in airway caliber (probably a small effect), and alteration in asthma medications (may have a large effect depending on the circumstances).
Finally, partial tolerance of methacholine may occur in nonasthmatic subjects but not in asthmatic subjects when tests arerepeated at less than 24-h intervals (184, 185). The observed
tolerance may have been related to the higher cumulative
doses of methacholine given to the nonasthmatic subjects (185).
III. EXERCISE CHALLENGE
Exercise induces airway narrowing in the majority of patientswith asthma. Exercise-induced airway narrowing is called exercise-induced asthma (EIA) and exercise-induced bronchoconstriction (EIB); the latter term is used here. The major
factors that determine severity of EIB are the pulmonary ventilation reached and sustained during exercise and the watercontent and temperature of the inspired air. The stimulus bywhich exercise causes the airways to narrow is the loss of water in bringing large volumes of air to body conditions in ashort time (I 86189). The mechanisms whereby water loss causes
the airways to narrow is thought to involve the thermal (cooling and rewarming) and/or osmotic effects (190-195) of dehydration. While airway cooling during exercise and airway rewarming after exercise are important determinants of the magnitude
of response in adults breathing air of subfreezing temperatures (190), they are not prerequisites for EIB (194). Thus,
EIB can occur when the inspired air temperature is greaterthan 37” C and in the absence of airway cooling (192,196-198).
Rapid rewarming does not enhance EIB in children (199).
Airway cooling and drying are thought to stimulate the release of inflammatory mediators, such as histamine and thecysteinyl leukotrienes (200-203). Thus, exercise has become
an important challenge method for assessing the effects of antiinflammatory and other asthma medications. Given the observations of EIB occurring both in cold and very hot inspired
air conditions, it can be concluded that, for the purposes of exercise challenges, the most important factor to control is therate of water loss from the airways by monitoring ventilationand controlling inspired water content.
A. Indications
Exercise is used as a challenge test to make a diagnosis of EIB
in asthmatic patients with a history of breathlessness during or
after exertion. Such a diagnosis cannot be made with a methacholine test and EIB cannot be excluded by a negative response
to methacholine. When the presence of EIB would impair theability of a person with a history suggesting asthma to performdemanding or lifesaving work (e.g., military, police, or firefighting work), a test for EIB may be indicated (204, 205). Exercise
testing is used to determine the effectiveness and optimal dosages of medications prescribed to prevent EIB. Exercise is also
used to evaluate the effects of antiinflammatory therapy given

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acutely (e.g., cromolyn sodium and nedocromil sodium) andchronically (e.g., steroids and leukotriene antagonists).
B. Contraindications and Patient Preparation
Contraindications. The contraindications for this test are thesame as for methacholine challenge testing (Table 1). In addition, the patient with unstable cardiac ischemia or malignant
arrhythmias should not be tested. Those with orthopedic limitation to exercise are unlikely to achieve exercise ventilationhigh enough to elicit airway narrowing. For patients over 60 yrold, a 12-lead electrocardiogram (ECG) obtained within thepast year should be available.
Patientpreparation. The patient should report to the laboratory in comfortable clothes and running or gym shoes, having
consumed no more than a light meal and having had pulmonary medications withdrawn as suggested (Table 2). In addition, antihistamines should have been withheld for 48 h. Vigorous exercise should be avoided for at least 4 h before testing, asprior exercise has been found to exert a protective effect. Theinterval between repeat testing must also be at least 4 h.
Rationale. Fifty percent of individuals with exercise-induced
bronchoconstriction are refractory to a second challenge within
60 min (206). Most lose this refractory state within 2 h. but it
occasionally takes as long as 4 h (207-210).

C. Exercise Challenge Testing
Modes of exercise. The preferred modes of exercise are themotor-driven treadmill with adjustable speed and grade or
the electromagnetically braked cycle ergometer. Heart rateshould be monitored from a three-lead electrocardiographic
configuration as a minimum. Alternatively, a pulse oximeteror other device able to reliably determine heart rate may be
used. For those at higher risk for coronary artery disease, a 12lead ECG configuration is advisable.
Inhalate. The patient inspires dry air less than 25” C with anoseclip in place, as nasal breathing decreases the water loss
from the airways (211). This can be accomplished by conducting the study in an air-conditioned room (with ambient temperature of 20-25” C) with low relative humidity (50% orless). Inspired air temperature and humidity should be measured and recorded. Optimally, the water content of the inspired air should be less than 10 mg/L. Alternatively, the subject can inspire dry air through a mouthpiece and a two-way
breathing valve. A dry inhalate is obtained by filling talc-free
meteorological balloons with gas from a medical-grade compressed air source (195, 212, 213). Dry air can also be inspired
through a demand valve attached to the inspired port of thetwo-way valve, although this provides some extra inspiratory
resistance at high flow rates (214).
Treadmill protocol. Treadmill speed and grade are chosen
to produce 4-6 min of exercise at near-maximum targets witha total duration of exercise of 6-8 min. For children less than
12 yr of age, the time is usually 6 min; for older children andadults the time is usually 8 min. Starting at a low speed andgrade, both are progressively advanced during the first 2-3
min of exercise until the heart rate is 80-90% of the predictedmaximum (calculated as 220 - age in years) (203, 210, 215217). Ventilation rather than heart rate can be used to monitor
exercise intensity. Ventilation should reach 4060% of thepredicted maximum voluntary ventilation (MVV, estimated as
FEV, X 35) (214,218,219). The degree of physical fitness andbody weight will strongly influence the grade and speed necessary to obtain the desired heart rate. A reasonable procedure
is to quickly advance to a rapid, but comfortable, speed andthen raise the treadmill slope until the desired heart rate or
ventilation is obtained. Treadmill speed and slope are chosenAmerican Thoracic Society

to achieve a target ventilation (or heart rate) that is maintained for at least 4 min. Children are usually able to reach thetarget more quickly than adults and for them the exercise duration may be only 6 or 7 min. For older children and adults
8 min of exercise is usually required to elicit EIB when dry air
temperature is inhaled. A treadmill speed greater than 3 mph(about 4.5 km/h) and a gradient greater than 15% or an oxygen consumption of 35 ml/min/kg or greater will usually achieve
the target ventilation or heart rate in young healthy subjects.
Nomograms have been proposed to predict speed and gradethat will elicit the desired heart rate (210) but they have notbeen extensively validated. It may be preferable to use nomograms relating oxygen consumption per kilogram to speed andslope of the treadmill (22@222).
The test ends when the patient has exercised at the target
ventilation or heart rate for at least 4 min. This usually requires a total of 6-8 min of exercise. The test may be terminated by the patient at any time.
Bicycfe ergometer. For bicycle ergometer exercise, a target
work rate to achieve the target ventilation can be determinedfrom equations relating work rate to oxygen consumption andoxygen consumption to ventilation (193,219,222). One equation used to establish the target work rate is watts = (53.76 X
measured FEV,) - 11.07. The work rate is set to 60% of thetarget in the first minute, 75% in the second minute, 90% in
the third minute, and 100% in the fourth minute (214). Using
this protocol the repeatability of the percent fall in FEV, isgood. For example, the coefficient of variation for two tests
performed within 1 mo is 21%. Thus, a patient who has a 30%
fall in FEV, on one occasion would be expected to have a fallwithin 24-36% if tested within 1 mo. Ventilation and/or heart
rate are checked to determine if the exercise targets areachieved. A valid test requires the target exercise intensity to
be sustained for 4-6 min. To ensure that the target minuteventilation is sustained, the work rate may need to be reducedin the final minutes of exercise. It is important for the patient
to reach the target heart rate or ventilation within 4 min because the rate of water loss is the determining factor for eliciting EIB and refractoriness can develop if exercise is prolonged at submaximal work. The test ends when the patient
has exercised at the target work rate for 6 min. The patient
may terminate the test at any time.
Pulmonary gas exchange. Measurement of pulmonary gas
exchange during exercise is helpful, although not required. Measurement of minute ventilation allows an assessment of themagnitude of the stimulus to airway narrowing (223) and measurement of oxygen uptake makes it possible to quantify theintensity of exercise as a fraction of predicted peak oxygen uptake. These data can be used to confirm an adequate exercise
level, which is especially important when a test is negative.
Safety. A licensed physician or an experienced technician
should observe the patient during exercise and the recovery
period and watch for undue stress (e.g., severe wheezing, chest
pain, lack of coordination) or adverse signs (e.g., ECG abnormalities, falling blood pressure, severe decrease in OZ saturation). The choice of who monitors the test and what parameters are monitored depends on the risk for adverse events. In
patients felt to be low risk for adverse events, the test may besupervised by an experienced technician, provided that a licensed physician can be summoned quickly, if problems arise.
The technician should be able to recognize the presence of indicators of respiratory distress and be able to recognize thepresence of significant arrhythmias. In patients felt to be at
higher risk for adverse events, a physician should directly monitor the test. In either case, a resuscitation cart should be immediately available.

321

Although not always accurate during exercise (224, 225)
estimation of arterial O2 saturation by pulse oximetry is recommended both during and after exercise. Measurement ofblood pressure by sphygmomanometry is a useful adjunct but
is not routinely required. ECG monitoring of all subjects isnecessary to ensure accurate heart rate measurements but 12lead monitoring is necessary only in high-risk cases.
Rationale. The choice of the recommended technique isbased on physiologic considerations and on substantial experience reported in the literature (1, 201,210, 213-215, 218, 219,
221,223,226-228).
Mode of exercise. Although early studies suggested that treadmill exercise was preferable to bicycle exercise (226,229,230),
it appears this was most likely due to the more rapid increasein ventilation in response to treadmill running. Providing thework rate can raise the ventilation to the target within 4 min,cycling exercise can be used effectively. Although peak oxygen uptake averages approximately 10% less on the cycle ergometer than on the treadmill, peak ventilation is comparable(231). In those with established EIB, the cycle ergometer has
been used successfully in assessing the effects of drugs (214).
Its role in identifying those with EIB is less well defined. Theoretically, cycle ergometry should be a satisfactory alternative
testing mode; well-designed comparative studies will be required to establish this. Free range running has been proposed
as being useful for screening populations (232-235), althoughsafety measures are difficult to provide in this testing mode.
Choice of the inhalate. The tendency to elicit airway narrowing is enhanced when the inhalate is cool and/or dry. However, it
is not clear whether the ambient humidity in the typical air-conditioned laboratory (typically 3&50% water vapor saturation) is
significantly less likely to induce airway narrowing than perfectly
dry air (as can be obtained from a compressed air source).
Anderson and coworkers (189) found in a group of 12 children a
35 + 13% (SD) fall in FEV, with ambient air (23.3” C, 12 mg
H,O/L) and a 45 + 16.7% (SD) fall in FEV, with compressed
dry air (25.4” C). Although the difference was not significant, thegreater response to compressed air may help to identify persons
with mild EIB and diminish the chance of a negative test. Coldair generators, which produce dry air at below-freezing temperatures, are commercially available and are in use in some laboratories (236). In patients in whom symptoms are specifically associated with exercise in the cold, conducting an exercise challenge
while breathing a cold dry inhalate may be useful.
Work rate profile. A range of testing configurations may
produce a similar degree of bronchoconstriction is susceptible
individuals. However, the target minute ventilation must be
reached quickly and be sustained for 4 min to diminish thepossibility that refractoriness will occur. The intensity of theexercise should be such that the person cannot exercise muchbeyond 6 or 8 min. If they can, it is unlikely that the workload
was sufficiently hard to elicit EIB. The incremental work rate
profile used in cardiopulmonary exercise testing, in which exercise intensity is progressively increased to tolerance over alo-min period (231) is less likely to be effective in evaluating
EIB (237) probably because high levels of ventilation are sustained for a relatively short time. Studies will be required toevaluate this possibility. The evidence suggests the most effective exercise is hard and relatively brief. Specifically, prolonging the warm-up period has the potential to induce refractoriness to EIB. Sustaining the heavy exercise period for a
prolonged period may actually diminish the bronchoconstriction; a trend for a decreased response has been demonstrated
for exercise periods of 12 min or longer (221).
Using a heart rate target is practical and generally effective. However, because pulmonary ventilation is more closely

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AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINE

related to the stimulus to bronchoconstriction than is heartrate, some authors prefer measuring ventilation to guide exercise intensity. Anderson and colleagues have suggested that
ventilation be sustained for 4 min at between 40 and 60% ofpredicted maximum voluntary ventilation, calculated as FEVl X
35 (214,218,219).
Safely. The most common problem encountered in exercisinga patient with asthma is severe bronchoconstriction. This canusually be treated rapidly and successfully by administering nebulized bronchodilator with oxygen. The appropriate equipment
should be immediately available and a pulse oximeter should be
kept on the subject. As the patients most likely to have the most
severe response are those with less than normal lung function aminimum FEV, for a patient to be allowed to proceed with theexercise test must be clearly defined. The European Respiratory
Society (219) suggested an FEV, greater than 75% of the predicted normal value.
The approach to monitoring will vary depending on the setting in which exercise testing is conducted and an assessment ofrisk for the individual being tested. Risk of adverse eventsshould be minimized and a rapid response should be available in
the event of a serious adverse event. In a hospital setting, wherea resuscitation team is readily available, a young, healthy subject
who has symptoms of exercise-induced bronchoconstriction canbe tested in a laboratory with minimum monitoring and only atechnician present. In a setting with less support and a higher
risk patient, more intense monitoring by individuals with theskills to appropriately diagnose and treat adverse events would
be necessary. In their procedure manual, testing laboratories
should define the appropriate levels of monitoring and the person who makes the decisions to test individual subjects.
D. Assessing the Response
Forced expiratory volume in 1 s (FEV,) is the primary outcome variable. Spirometry should be performed in the seatedposition before exercise and then serially after exercise, utilizing the test method recommended by the American Thoracic
Society (120). At least two and preferably three acceptable
tests should be obtained at each testing interval. As a goal, thehighest and second highest FEV, values should differ by no
more than 0.2 L. The highest of the acceptable FEV, values isselected as the representative value at each interval. One exception to ATS-recommended techniques for spirometry is allowed. If the only outcome variable to be used is the FEV,,the duration of the expiration may be limited to 2-3 s. In allcases it is important to vigorously coach the patient to inhale
fully even in the presence of chest tightness. Incomplete inhalations will result in false reductions in FEV,.
If vocal cord dysfunction or other possible causes of central
airway obstruction are suspected, full inspiratory and expiratory flow-volume loops should be obtained.
An appropriate postexercise testing schedule is 5, 10, 15, 20,
and 30 min after cessation of exercise. Some investigators include earlier measurements (1 and 3 min postexercise) because
severe EIB can sometimes be present at the cessation of exercise(214,219). Early recognition allows it to be dealt with promptly.
If the FEV, has returned from its nadir to the baseline levelor greater, spirometry testing may be terminated at 20 min
postexercise. A P-agonist bronchodilator may be administeredat any time to reverse the bronchoconstrictive response if thepatient experiences appreciable dyspnea, or if the FEV, has
not recovered to within 10% of baseline when the patient isready to leave the laboratory.
The presence of exercise-induced bronchoconstriction isdefined by plotting FEV, as a percentage of the preexercise
baseline FEV, at each postexercise interval. A decrease below

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90% of the baseline FEV, (i.e., a 10% decrease) is a generally
accepted abnormal response (1,218,221,237-240). Some authors suggest a value of 15% is more diagnostic of EIB, particularly if exercise has been performed in the field (233).
Rationale. A large number of testing schedules for performing postexercise spirometry have been suggested. In mostcases, the nadir in FEV, occurs within S-10 min of cessation of
exercise, although it is occasionally not reached until 30 min
postexercise (239). Including a 30-minute postexercise observation is controversial, because such a delay is infrequently
seen. Some laboratories terminate the test as soon as the
FEV, falls below a certain threshold (e.g., 10%). Without confirming the FEV, has reached its nadir, it is not possible toassess the severity of exercise-induced bronchoconstriction.
Other laboratories define the nadir as when the FEV, has increased from its lowest value at the two subsequent time intervals (e.g., the test is terminated at 15 min when the lo- and 15
min FEV, values are higher than that measured at 5 min). This
reduces the time of challenge for most patients.
The criterion for a positive response is controversial. A fallof 10% or more is considered abnormal; a fall of 15% appears
to be more diagnostic of EIB. A fall in FEV, of as little as
10% seems to be a reasonable criterion because healthy subjects generally demonstrate an increase in FEV, after exercise.
Some authors have employed a more stringent criterion (e.g.,
a 15% fall) (223, 227). Three studies in presumably normalchildren have demonstrated an upper 95% confidence limit(defined as 1.96 SD) of the FEV, fall as 8.2% (241), 10%(242), and 15.3% (233). Further studies are needed to establish the validity of proposed thresholds for a positive test.
A positive response is seen in those with upper airway abnormalities such as abnormal posterior motion of the arytenoid
region (243) or vocal cord dysfunction (244). These rare cases
can be distinguished from exercise-induced bronchoconstriction by examining the flow-volume curve (245,246).
ATS Committee on Proficiency Standards for Clinical Pulmonary
Function Laboratories
Committee Members
R OBERT 0. CFZAPO, M.D., Choirman
RICHARD CASABURI, Ph.D., M.D.
ALV\N L. COATES, M.D.
PAUL L. ENRIGHT, M.D
JOHN L. HANKINSON , Ph.D.
CHARLES G. IRVIN, Ph.D.
NEIL R. MAC~NTYRE, M.D.
ROY T. MCKAY, Ph.D.
JASK 5. WANGER , M.S.

Ad Hoc Committee Members
SANDRA D. ANDERSON, Ph.D.
DON W. COCKCROFT, M.D.
JAMES E. FISH, M.D.
PETER J. STERK, M.D.

Acknowledgment: The authors thank janet Emby for editorial assistance.
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1160. Weeke, B., F. Madsen, and L. Frolund. 1987. Reproducibility of challenge tests at different times [Review]. Chesf 91(Suppl. 6):83S-89s.
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208. Edmunds, A. T., M. Tooley, and S. Godfrey. 1978. The refractory period after exercise-induced asthma: its duration and relation to theseverity of exercise. Am. Rev. Respir. Dis. 117:247-254.
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328

AMERICAN JOURNAL OF RESPIRATORY AND CRITICAL CARE MEDICINEAPPENDIX ASAMPLE METHACHOLINE CHALLENGE TEST CONSENT FORM

PROCEDURE. The purpose of a methacholine challenge test is to determine the amount of

airway irritability of a patient. You (or your child) will be asked to inhale a mist that contains
different concentrations of methacholine. The mist is produced by a device called a nebulizer andinhaled through a mouthpiece or facemask. Before the test begins, and after each period of
inhalation, you or your child will be asked to blow forcefully into a spirometer. The test usuallytakes about an hour.
DISCOMFORTS AND RISKS. This test does not cause an asthma attack but the inhalation ofaerosols may be associated with mild shortness of breath, caught, chest tightness, wheezing,chest soreness, or headache. Many subjects do not have any symptoms at all. These symptoms (ifthey occur) are mild, last for only a few minutes, and disappear following the inhalation of a bronchodilator medication. There is a very small possibility of severe narrowing of your airways. This
could cause severe shortness of breath. If this occurs, you will be immediately treated.
I have read the above information and undertsand the purpose of the test and the associated risks.
With this knowledge I agree to having this test performed on me or my child.

Patient or Guardian

Date

Witness

Date

APPENDIX BSAMPLE METHACHOLINE CHALLENGE PRETEST QUESTIONNAIRE

Name:

Date of birth:

1. List all medications you have taken in the last 48 hours for asthma, hay fever, heart disease,
blood pressure, allergies, or stomach problems, and the number of hours or days since yourlast dose for each medication.
Drug

Date and time of last treatment

2. Has a physician told you that you have asthma?
3. Have you ever been hospitalized for asthma?
4. Did you have respiratory disease as a child?
5. Have you ever experienced asthma symptoms suchas wheezing, chest tightness, or shortness of breath
within the last two weeks?
6. If a smoker, when did you last smoke?
7. Have you had a respiratory infection in the last 6 weeks?
8. Have you had a heart attack or stroke within the last three months?
9. Do you have high blood pressure?
10. Do you have an aortic aneurysm?
11. Are you pregnant?

Yes
Yes
Yes

No
No
No

Yes

No

Yes
Yes
Yes
Yes
Yes

No
No
No
No
No

VOL 161

2000

329

American Thoracic Society
APPENDIX CSAMPLE METHACHOLINECHALLENGE TEST REPORT FORM

Laboratory name, address, and phone number:
Patient name, ID number, date of birth, sex, height:
Test date, technician initials:
Indication for the test (e.g., rule out asthma):
Test method (e.g., five-breath dosimeter):Bronchodilator administered and dose:Time

Test Phased FEVlQC
FEV, Score (% of baseline)

9:00 Baseline
3.10
9:lO Diluent
3.00
9:15 0.06 mg/ml
3.05
9:20 0.25 mg/ml
2.94
9:25
2.62
1 .O mg/ml
9:30 4 . 0 mg/ml
2.16
9:45 BD recovery 3.20

A
B
A
C
A
A
B

100%
102%
98%
8796
72%
107%

(display tlow-volume or volume-time CWW)

Bronchial responsiveness: PCzO 1=9 mg/ml (insert or attach a dose-response curve)
Signs and symptoms after final dose: Chest tightness, wheezing.
Symptoms completely resolved after bronchodilator (BD)Interpretation: Test quality is acceptable
Mild bronchial hyperresponsiveness
Medical director’s signature:

APPENDIX DEQUIPMENT SOURCES*
Equipment

Company
DeVilbiss Health Care, Inc.
P.O. Box 635
Somerset, PA 15501-0635(814) 443-4881

DeVilbiss 646 nebulizers

Mallinckrodt
675 McDonnell Blvd.
Hazelwood, MO 63042(800) 635-5267
http://malinckrodt.com

Nebulizers

Marquest Medical Products
11039 E. Lansing Circle
Englewood, CO 80112(303) 790-4835
http://www.marquestmedical.com

Filters

Matheson Tri-Gas
166 Keystone Drive
Montgometyville, PA 18936
http://www.mathesongas.com

Gas meters
Rotameters

Methapharm Inc.
131 Clarence St.
Brantford, Ontario N3T 2V6, Canada(800) 287-7686
http://www.metapharm.com

Methocholine (Provocholine)

Pall Biomedical Products Corporation
2200 Northern Blvd.
East Hills, NY 1 1548
http://www.pall.com

Filters

PDS Instrumentation
908 Main Street
Louisville, CO 80027(303) 666-8100
http://www.pulmonarydata.com

Dosimeters
Methocholine (Provocholine)
DeVilbiss 646 nebulizers, output characterizedwith a flow regulator
Filters

Roxon Medi-Tech
a500 Lafrenaie
Montreal, Quebec Hl P 284, Canada(514) 326-7780
http://www.biomed.nicolet.com

English Wright nebulizer

Filters* This list is provided to simplify access to some sources of equipment. It is not a complete list of all possible sources of acceptable equipment.