What is the appropriate evaluation and management for a patient with a persistent cough lasting two months?

Evaluation and Management of Persistent Cough (Two Months Duration)

A cough lasting two months is classified as subacute cough (3-8 weeks), most commonly post-infectious in origin, and should be treated initially with inhaled ipratropium bromide while ruling out pertussis if paroxysmal features are present. 1, 2

Initial Mandatory Assessment

Red Flag Evaluation

• Immediately assess for hemoptysis, fever, night sweats, weight loss, or history of tuberculosis, cancer, or AIDS—these require urgent expanded workup 3, 4
• In smokers, examine for finger clubbing with pleural effusion or lobar collapse, which strongly suggests bronchogenic carcinoma 1
• Cough is the fourth most common presenting feature of lung cancer 1

Essential Baseline Investigations

• Obtain chest radiograph in all patients with cough lasting >2 weeks to exclude pneumonia, malignancy, tuberculosis, bronchiectasis, and interstitial lung disease 1, 3, 4
  • Approximately 31% of chest radiographs in persistent cough will be abnormal or yield a diagnosis 1, 4
• Perform spirometry with bronchodilator response testing in all patients 1, 4
  • Measure FEV1 before and after short-acting β2-agonist (salbutamol 400 mcg by MDI with spacer or 2.5 mg nebulized) 1
  • Normal spirometry does NOT exclude asthma or eosinophilic bronchitis 1, 4

Geographic and Risk-Based Testing

• If paroxysmal cough, post-tussive vomiting, or inspiratory whooping present, obtain nasopharyngeal culture for Bordetella pertussis 4, 2
  • Pertussis accounts for approximately 10% of chronic cough cases in some series 1, 4
  • If confirmed, treat with macrolide antibiotics 2
• In high TB prevalence areas, obtain sputum smears and cultures for acid-fast bacilli 4

Treatment Algorithm for Subacute Cough (2 Months = 8 Weeks)

First-Line Therapy: Post-Infectious Cough

• Prescribe inhaled ipratropium bromide as first-line therapy—it has demonstrated efficacy in controlled trials for post-infectious cough 2
• Provide reassurance that post-infectious cough typically resolves spontaneously within 3-8 weeks total from symptom onset 2
• Do NOT prescribe antibiotics unless bacterial sinusitis or pertussis is confirmed—bacterial infection does not play a role in post-infectious cough pathogenesis 2

Transition to Chronic Cough Evaluation (If Persists Beyond 8 Weeks)

At exactly 8 weeks total duration, the cough becomes chronic and requires systematic evaluation 1, 2:

Step 1: Upper Airway Cough Syndrome (UACS)

• Initiate empiric therapy with first-generation antihistamine-decongestant combination for 1-2 weeks 3, 2
• Clinical pointers: nasal discharge, throat clearing, postnasal drip sensation, nasal congestion, or rhinorrhea 3

Step 2: Asthma Evaluation (If UACS Treatment Fails)

• Suspect when cough worsens at night, with cold air exposure, or with exercise 3
• If normal spirometry and bronchodilator response but asthma or eosinophilic bronchitis suspected, offer therapeutic trial of prednisolone 30-40 mg daily for 2 weeks 1, 4
• Response to bronchodilators may occur within 1 week, but complete resolution can take up to 8 weeks 3

Step 3: GERD Therapy (If Both UACS and Asthma Treatments Fail)

• Initiate intensive GERD therapy including high-dose PPI, dietary modifications, and lifestyle changes 3, 2
• Critical caveat: GERD therapy requires patience—response may take 2 weeks to several months, with some patients requiring 8-12 weeks before improvement 3
• Minimum treatment duration is 2 months 4

Advanced Diagnostic Testing (Only After Adequate Therapeutic Trials Fail)

Proceed to advanced testing only after adequate trials of UACS, asthma, and GERD have failed 3:

• High-resolution CT chest to evaluate for bronchiectasis, interstitial lung disease, or occult masses 3
• 24-hour esophageal pH monitoring if empiric GERD therapy failed 3
• Bronchoscopy to evaluate for endobronchial lesions, sarcoidosis, eosinophilic bronchitis, or occult infection 3

Management of Truly Refractory Chronic Cough

Only diagnose unexplained cough after completing systematic evaluation and adequate therapeutic trials of all common causes 3:

• Consider gabapentin trial starting at 300 mg once daily, escalating as tolerated to maximum 1,800 mg daily in divided doses 3
• Multimodality speech pathology therapy is a reasonable alternative 3
• Low-dose morphine may be considered but carries addiction risk 3

Critical Pitfalls to Avoid

• Do NOT use single peak flow measurements for diagnosis—they are less accurate than FEV1 for identifying airflow obstruction 1, 4
• Do NOT fail to recognize the 8-week threshold where post-infectious cough becomes chronic cough requiring different evaluation 2
• Do NOT inappropriately prescribe antibiotics for non-bacterial post-infectious cough 2
• Do NOT abandon GERD therapy prematurely—it may require 8-12 weeks for response 3

Common Causes by Setting

In primary care, 46% of patients with cough >2 weeks have asthma or COPD 1. In specialist centers, the most common causes are gastroesophageal reflux, cough-predominant asthma, and rhinitis 1, 5, 6.