INDICATIONS AND USAGE
Standardized Mite allergenic extract is indicated for diagnostic testing and for the treatment (immunotherapy) of patients whose histories indicate that upon natural exposure to the allergen, they experience allergic symptoms. Confirmation is determined by skin testing. An orderly approach to the diagnostic use of allergenic extracts usually begins with direct skin testing. This product is not intended for treatment of patients who do not manifest immediate hypersensitivity reactions to the allergenic extract following skin testing.
Mite mixtures should not be used for diagnostic skin testing. The individual mites should be used. Mite mixtures may be used for immunotherapy to treat patients who demonstrated sensitivity to both D. farinae and D. pteronyssinus mites. Patients who react to both D. farinae and D. pteronyssinus have demonstrated a significant cross-reactivity. Caution should be used in escalating treatment with mite mixtures.21
PRICK-PUNCTURE TESTING: A positive control using Histamine Phosphate is important to identify those patients whose skin may not be reactive due to medications, metabolic or other reasons. A diluent control, if negative, would exclude false-positive reactions due to ingredients in the diluent or patients who have dermatographism.
To identify highly sensitive individuals and as a safety precaution, it is recommended that prick-puncture test using a drop of the extract concentrate (10,000 AU/ml) be performed prior to initiating very dilute intradermal testing. Prick-puncture testing is performed by placing a drop of extract concentrate on the skin and puncturing the skin through the drop with a small needle such as a bifurcated vaccinating needle. The most satisfactory sites on the back for skin testing are from the posterior axillary fold to 2.5 cm from the spinal column, and from the top of the scapula to the lower rib margins. The best areas on the arms are the volar surfaces from the axilla to 2.5 or 5 cm above the wrist, skipping the anticubital space. Glycerinated Mite extracts containing 10,000 AU/ml are recommended for prick-puncture testing. Skin reactions are based on size of erythema and wheal. For interpretation of skin reactions, refer to chart below.
GRADE
mm ERYTHEMA
mm WHEAL
0
less than 5
less than 5
+/-
5-10
5-10
1+
11-20
5-10
2+
20-30
5-10
3+
31-40
10-15or with pseudopods
4+
greater than 40
greater than 15or with many pseudopods
Smaller, less conclusive reactions may be considered positive in conjunction with a definitive history of symptoms on exposure to the mite allergen. The more sensitive the patient the higher the probability that he/she will have symptoms related to the exposure of the offending allergen. Hence, the importance of a good patient history. Less sensitive individuals can be tested intradermally with an appropriately diluted extract.
A clinical study using the same patients with positive prick-puncture test (10) using the ID50EAL Method, Intradermal Dilution for 50 mm Sum of Erythema D50 Determines the Allergy Unit, has demonstrated the following:
Skin test by prick-puncture test using Standardized D. farinae Mite, 10,000 AU/ml was performed in 10 patients. The mean sum of erythema diameter was 76.6 mm (Range 45-104 mm). Skin test by prick-puncture test using Standardized D. pteronyssinus Mite, 10,000 AU/ml in 10 patients, the mean sum of erythema diameter was 74.7 mm (Range 43-109 mm).
TABLE 1STANDARDIZED MITE ALLERGENIC EXTRACTSLABELED 10,000 AU/ml
10,000 AU/ml1:3 Dilutions
10,000 AU/ml1:5 Dilutions
10,000 AU/ml1:10 Dilutions
*C 10,000 3-1 3,333 3-2 1,111 3-3 370.37 3-4 123.45 3-5 41.15 3-6 13.71 3-7 4.57 3-8 1.52 3-9 0.508 3-10 0.169 3-11 0.056 3-12 0.018
3-13 0.0063 3-14 0.0021 3-15 0.0007
*C 10,000 5-1 2,000 5-2 400 5-3 80 5-4 16 5-5 3.20 5-6 0.64 5-7 0.128 5-8 0.0256
5-9 0.00512 5-10 0.00102
*C 10,000 10-1 1,000 10-2 100 10-3 10 10-4 1 10-5 0.10 10-6 0.01
10-7 0.001 10-8 0.0001 10-9 0.00001
*C = Concentration
SINGLE DILUTION INTRADERMAL TESTING: The surface of the upper and lower arm is the usual location for skin testing. It is important that a new, sterile, disposable syringe and needle be used for each extract tested. Intracutaneous test dilutions should be made with aqueous diluent. (1) Start testing with the most dilute allergenic extract concentration. (2) A volume of 0.02-0.05 ml should be injected slowly into the superficial skin layers making a small bleb (superficial wheal). (3) For patients without a history of extreme sensitivity, a prick-puncture test of less than 2+, the initial dilution for skin testing should contain 0.02 to 0.06 AU/ml (see Table I). For very sensitive patients with a prick-puncture of greater than 2+, a further dilution should be made to 0.002 to 0.006 AU/ml (see Table I). If after 20 minutes no skin reaction is obtained, continue the testing using five-fold or ten-fold increments in potency until a reaction of 1+ or until the concentration of 2,000 AU (five-fold) or 1,000 AU (ten-fold) has been tested with a glycerine control. Glycerine may be used at a dilution of 0.5% as long as 0.5% glycerine produces negative control. The diluent should be tested and included in the interpretation of the skin reactions.16
INTRADERMAL TESTINGSKIN ENDPOINT TITRATION: The allergenic extracts to which the patient is sensitive, the patient's degree of sensitivity and the dose of allergen to be used in immunotherapy can be determined through the use of intracutaneous skin tests involving progressive five-fold dilutions of allergenic extracts, prepared and refrigerated at 2-8 C. The critical variable is the size if the wheal and erythema produced by the intracutaneous injection of 0.01 to 0.02 ml of the test allergen producing a 4 mm diameter superficial skin wheal. For patients demonstrating a prick-puncture skin test of less than 2+, an initial screening dilution of 0.02-0.06 AU/ml is safe (see Table I). For patients demonstrating a prick-puncture skin test greater than 2+, an initial screening dilution of 0.002 to 0.006 AU/ml is safe. The skin endpoint is detected by noting the dilution that produces a wheal 2 mm larger than non-reacting dilutions (5 mm negative wheal) until progressive whealing with each five-fold increase in test potency occurs, i.e., a 5 mm (negative), 7 mm, 9 mm, 11 mm is the normal sequence of whealing. The 7 mm wheal would be the endpoint. The endpoint dilution is used as an initial dose concentration for immunotherapy. An endpoint dose of 0.15 ml is a safe initial dose to be followed by escalation to the optimal maximum tolerated dose for each individual.
Using Standardized D. farinae Mite, 10,000 AU/ml on 10 patients, the mean AU for 50 mm sum of erythema was 0.02 AU (Standard deviation was 1.4). Using Standardized D. pteronyssinus Mite 10,000 AU/ml in 10 patients, the mean AU for 50 mm sum of erythema was 0.02 AU (Standard deviation was 1.7).