Diagnostic Approach for Chronic Cough

Initial Mandatory Investigations

Chest radiograph is required for all patients with chronic cough to rule out significant pathology such as malignancy, infection, or structural abnormalities 1, 2, 3
Spirometry with bronchodilator response is essential to identify airflow obstruction and assess for reversibility that might indicate asthma 1, 4, 5
Detailed history and physical examination should focus on the common causes of chronic cough and potential aggravating factors 1, 2
Assessment of cough severity and impact on quality of life using validated tools such as cough visual analogue scores or cough-specific quality of life questionnaires is recommended 1, 4

Bronchial provocation testing should be performed in patients with normal spirometry referred to a respiratory physician 1, 4, 6
A two-week trial of oral corticosteroids can help diagnose eosinophilic airway inflammation; lack of response effectively rules it out 1, 4, 6

An empiric treatment trial is often preferred over diagnostic testing as initial approach 7
24-hour esophageal pH monitoring may be considered if empiric treatment fails 7

All patients on ACE inhibitors should discontinue these medications as they are a common cause of chronic cough 1, 4, 6
Smoking cessation should be strongly encouraged as it can lead to significant improvement in cough symptoms 1, 4, 8
A thorough occupational history is essential to identify potential environmental triggers 1, 4

Overlooking GERD, as reflux-associated cough may occur without typical gastrointestinal symptoms 1, 4, 7
Inadequate trial periods for empiric therapy, as GERD treatment requires at least 3 months of intensive acid suppression for proper evaluation 1, 4
Relying solely on spirometry to diagnose asthma, as cough variant asthma may present with normal spirometry 4, 5

Chronic cough should only be labeled as idiopathic after thorough assessment at a specialist cough clinic 1, 4

The American College of Chest Physicians suggests that despite normal baseline investigations, the absence of abnormalities on chest X-ray and spirometry does not exclude disease, as both tests are specific but not sensitive 9
The three most common causes of chronic cough in adults with normal chest radiographs are upper airway cough syndrome (UACS), asthma, and gastroesophageal reflux disease (GERD), accounting for the vast majority of cases 10

The American College of Chest Physicians recommends beginning with a first-generation antihistamine-decongestant combination as UACS is the most common cause, with a typical response time of at least 1-2 weeks 10
If UACS treatment fails, proceed with bronchial provocation testing (methacholine challenge) to assess for bronchial hyperresponsiveness, as cough-variant asthma commonly presents with normal spirometry 11
A negative methacholine challenge essentially excludes asthma from the differential, according to the American College of Chest Physicians 11
If methacholine testing is unavailable, a 2-week trial of oral corticosteroids (e.g., prednisone) can confirm eosinophilic airway inflammation if cough improves, as suggested by the American College of Chest Physicians 12

Chronic cough is frequently multifactorial, with patients commonly having two or even all three of the common diagnoses (UACS, asthma, GERD) simultaneously, and the cough will not resolve until all contributing factors are effectively treated, according to the American College of Chest Physicians 10

Consider further diagnostic workup if the patient is immunocompromised or from a tuberculosis-endemic area, as recommended by the American College of Chest Physicians 10
Additional investigations may include high-resolution CT chest to evaluate for bronchiectasis, interstitial lung disease, or occult malignancy, as suggested by the American College of Chest Physicians 12
Bronchoscopy may be considered if structural abnormalities or endobronchial lesions are suspected, according to the American College of Chest Physicians 10