MCT and Capsaicin Provocation Challenge in Diagnosis of Chronic Cough
MCT and Capsaicin Provocation Challenge in Diagnosis of Chronic Cough
The aim of the study is to assess the prevalence of bronchial hyperresponsiveness (BHR) in
 non-smoking adults with chronic cough and the prevalence of BHR in patients with upper airway
 cough syndrome (UACS) and gastroesophageal reflux disease (GERD), to evaluate the
 relationship between BHR and cough reflex sensitivity, to assess the diagnostic accuracy of
 methacholine challenge test (MCT) in cough variant asthma (CVA) with special regard to its
 discriminating cut off value between CVA and other causes of chronic cough, particularly
 GERD, to estimate prognostic value of BHR, fractional exhaled nitric oxide (FeNO) and induced
 sputum eosinophil count in predicting response to asthma treatment.

 Patients diagnosed with a chronic cough will undergo the standard diagnostic work-up
 recommended by experts for patients with a chronic cough, including methacholine challenge
 test (MCT) and an at least 4-week period of causal treatment. Patients with BHR in MCT will
 be treated with - in first step B2-agonist and inhaled corticosteroid (ICS) for at least 4
 weeks, if improvement is not significant in next steps with leukotriene receptor antagonist
 (LTRA) or systemic corticosteroid. A good treatment response, evaluated by visual analogue
 scale (VAS), Leicester Cough Questionnaire (LCQ) and cough challenge will confirm the
 diagnosis of the disease. A statistical analysis will consist of the frequency of BHR in a
 chronic cough, correlation between the results of MCT and cough reflex sensitivity in
 capsaicin inhalation test and cut-off point for MCT to discriminate asthma from other causes
 of a chronic cough.
The present study has the following objectives:

 1. to assess the prevalence of BHR in non-smoking adults with a chronic cough,

 2. to assess the prevalence of BHR in patients with UACS and GERD,

 3. to evaluate the relationship between BHR and cough reflex sensitivity,

 4. to assess the diagnostic accuracy of MCT in CVA with special regard to its
 discriminating value between CVA and other causes of a chronic cough, particularly GERD,

 5. to estimate prognostic value of BHR, fractional exhaled nitric oxide (FeNO) and induced
 sputum eosinophil count in predicting response to asthma treatment.

 The investigated group will consist of 80 non-smoking adults (18-75 years old), who are not
 treated with angiotensin-converting enzyme inhibitors, with no signs of respiratory infection
 within six weeks prior to enrolment, with a normal chest radiograph and who are referred to
 the hospital due to a cough lasting at least eight weeks.

 After obtaining an informed consent, the diagnostic approach of the most common causes of
 chronic cough will be performed: a medical history, physical examination, chest radiograph,
 in some cases chest computed tomography, pulmonary function tests (spirometry, fractional
 exhaled nitric oxide, methacholine challenge test), laboratory tests (total immunoglobulin E
 concentration, complete blood count), skin prick tests, induced sputum cell count, computed
 tomography of the paranasal sinuses and ENT consultation, 24-hour impedance with pH
 monitoring, videolaryngoscopy and cough challenge with capsaicin.

 The cough severity will be assessed twice (on admission and after six weeks of causal
 treatment) using the Visual Analogue Scale (VAS), the Polish version of the Leicester Cough
 Questionnaire (LCQ) and the capsaicin inhalation cough challenge.

 If MCT result is positive, CVA will be assumed the cause of a chronic cough and treatment
 with an inhaled steroid combined with a long-acting beta-agonist will be administered for at
 least 4 weeks. If no satisfactory response to this treatment is observed, an anti-leukotriene
 agent or in the next step systemic corticosteroid will be applied. Ineffective treatment with
 the above-mentioned medications will indicate an opportunity for a different underlying cause
 of BHR. The estimation the area under a ROC (receiver operating characteristic) curve will be
 used to determine the optimal cut-off point for the differentiation between asthma and
 alternate causes of a chronic cough.

 It is expected to assess the frequency of bronchial hyperresponsiveness in subjects with a
 chronic cough, to confirm a correlation between the results of MCT and the sensitivity of
 cough reflex measured in capsaicin inhalation cough challenge. The investigation will
 probably determine a precise cut-off point for MCT which would allow discriminating asthma
 from other causes of a chronic cough.
Inclusion Criteria:

 1. Adults patients aged between 18 and 75;

 2. Chronic cough lasting more than 8 weeks;

 3. Non-smoking (min. 6 months);

 4. Not treated with angiotensin-converting enzyme (ACE) inhibitors;

 5. Not treated with:

 1. inhaled corticosteroids or systemic corticosteroids min. 4 weeks before
 enrolment,

 2. proton pump inhibitors min. 2 weeks before enrolment,

 3. antihistaminic drugs 1 week before enrolment;

 6. With normal chest radiograph or with insignificant changes in cough pathogenesis

 7. Without airway infection in previous 6 weeks.

 8. Patients enrolled with informed consent.

 Exclusion Criteria:

 1. Patients under 18 years old and above 75 years old;

 2. Smokers (actual or ex-smokers shorter than 6 weeks);

 3. Therapy with corticosteroids (inhaled or systemic) for last 4 weeks, proton pump
 inhibitors for 2 weeks, antihistaminic drug for 1 week before enrolment;

 4. Airway infection 6 weeks preceding enrolment or during study - re-attempt to enroll
 after 6 weeks