ATP and Capsaicin Cough Provocation Test in Chronic Cough and Bronchiectasis

Study Overview
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Brief Summary
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This is a randomized, cross-over, single-blind trial. Eligible patients will be randomly assigned to undergo either capsaicin or adenosine triphosphate (ATP) cough provocation test, followed by a washout period of 2 to 14 days. Participants will be crossed-over to undergo another cough provocation test. Patient would be under observation in the out-patient clinics for  2 hours following the cough provocation tests in case of severe adverse events.

Detailed Description
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This is a randomized, cross-over, single-blind trial. After verification of the entry criteria, eligible patients will be, based on the randomization codes, randomly assigned to undergo either capsaicin or ATP cough provocation test (the participants will inhale capasaicin or ATP incremental concentration to induce cough, meanwhile the number of coughs and adverse events will be recorded in each concentration during the first 30 seconds), followed by a washout period of 2 to 14 days (no major changes in the use of concomitant medications are allowed,especially the medcines which are not allowed before test ). Participants will be crossed-over to undergo another cough provocation test. Patient would be under observation in the out-patient clinics for  2 hours following the cough provocation tests in case of severe adverse events. Twenty four hours after each test, a follow-up telephone visit will be scheduled for all patients to record any response which may be related to the test.

Official Title
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Adenosine Triphosphate and Capsaicin Cough Provocation Test for Identifing Patients With Chronic Cough Who Have Differential Responses to Purinergic Receptor Antagonists: a Randomized, Cross-over, Single-blind Trial

Conditions
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Chronic Cough, Bronchiectasis

Intervention / Treatment
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* Diagnostic Test: Adenosine Triphosphate
* Diagnostic Test: capsaicin


Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: Out-patients of either gender, ex- or never-smokers, aged between 18 and 60 years Cough symptoms lasting for more than 8 weeks Remaining free of acute upper respiratory tract infection for at least 4 weeks Agreed to participate in the trial and signed informed consent. Exclusion Criteria: Patients with serious systemic diseases (such as malignant tumors), bullae, severe uncontrolled asthma, and a history of major hemoptysis Systemic antibiotic use (except for maintenance low-dose macrolides) within 4 weeks Pregnancy or lactation Any known history of sensitivity to ATP or capsaicin Poor understanding of the test procedure Diagnosed with cough variant asthma or Eosinophilic bronchitis

Ages Eligible for Study
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Minimum Age: 18 Years
Maximum Age: 60 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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Accepts Healthy Volunteers

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Chronic cough<br>patients with chronic cough who remain clinically stable | Diagnostic Test: Adenosine Triphosphate<br>* Adenosine Triphosphate aerosol<br>Diagnostic Test: capsaicin<br>* capsaicin aerosol<br>|
| Bx<br>bronchiectasis patients who remain clinically stable | Diagnostic Test: Adenosine Triphosphate<br>* Adenosine Triphosphate aerosol<br>Diagnostic Test: capsaicin<br>* capsaicin aerosol<br>|
| Control<br>healthy controls | Diagnostic Test: Adenosine Triphosphate<br>* Adenosine Triphosphate aerosol<br>Diagnostic Test: capsaicin<br>* capsaicin aerosol<br>|

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| C5 (Provocant concentration eliciting at least 5 coughs) | Provocant concentration eliciting at least 5 coughs | 18 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| ED50 (half maximal effective Dose) | 50% effective dose of provocant | 18 months | 
| Emax (effective concentration of provocant eliciting maximal cough count) | effective concentration of provocant eliciting maximal cough count | 18 months | 
| potency ratio | ATP/capsaicin potency ratio | 18 months | 
| Difference in cough VAS score (a 10-point likert scale for assessing the global severity of cough, no subscale was applied) | The difference between pre- and post-challenge cough VAS scores | 18 months | 
| The incidence of adverse events (i.e. dry throat , pharyngeal itching) | adverse events such as dry throat , pharyngeal itching, wheeze or dyspnea according to the subject's reporting to record the rate of the incidence and the severity (the aboved-mentioned VAS score would be applied) | 18 months | 
| Cough dose ratio (CDR) | the ratio of cough count and dose/concentration | 18 months | 

 Terms related to the study
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Keywords Provided by Centre Hospitalier Valida
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Adenosine triphosphate, Capsaicin, cough provocation test