How should I evaluate and manage a chronic cough lasting ≥8 weeks, including assessment for red‑flag features and reversible causes such as smoking, ACE‑inhibitor use, post‑nasal drip, gastro‑oesophageal reflux, and asthma?

Evaluation and Management of Chronic Cough (≥8 Weeks)

Begin by discontinuing any ACE inhibitor immediately—cough resolves within a median of 26 days in most patients—and advise smoking cessation, as smoking-related cough improves within 4 weeks in 90–100% of cases. 1, 2

Initial Red-Flag Assessment

Screen for the following features that mandate urgent investigation before routine algorithmic work-up:

• Hemoptysis – indicates possible malignancy, tuberculosis, bronchiectasis, or pulmonary embolism 3, 1
• Unintentional weight loss or fever – suggests malignancy, tuberculosis, or chronic infection 1, 2, 4
• Smoker ≥45 years with new or changed cough – requires immediate lung cancer evaluation 1
• Adults 55–80 years with ≥30 pack-year history (current smoker or quit within 15 years) – meets lung cancer screening criteria 1
• Prominent dyspnea at rest or nocturnal – signals severe cardiopulmonary disease 1, 2
• Hoarseness or dysphagia – may reflect laryngeal pathology or recurrent laryngeal nerve involvement 1, 2
• Recurrent pneumonia – points to structural lung disease, immunodeficiency, or aspiration 1, 2

Mandatory Baseline Investigations

Obtain chest radiograph and spirometry with bronchodilator testing in every patient with chronic cough—these are non-negotiable baseline studies. 3, 1, 5

Additional baseline testing should include:

• Cough severity quantification using visual analog scales or validated quality-of-life questionnaires to objectively monitor treatment response 3, 1
• Exhaled nitric oxide and blood eosinophil count to identify eosinophilic airway inflammation 5

Systematic Empiric Treatment Algorithm

The "Big Four" etiologies—upper airway cough syndrome (UACS), asthma, gastroesophageal reflux disease (GERD), and nonasthmatic eosinophilic bronchitis (NAEB)—account for >90% of chronic cough cases in nonsmokers with normal or near-normal chest radiographs. 3, 1, 6, 7 Critically, up to 67% of patients have multiple simultaneous causes, requiring combination therapy rather than sequential monotherapy. 1, 2

Step 1: Upper Airway Cough Syndrome (UACS)

UACS is the single most common cause, accounting for 19–82% of chronic cough cases. 3, 1, 2

• Initiate first-generation antihistamine-decongestant combination therapy as the initial empiric treatment 1, 6
• Look for post-nasal drip sensation, frequent throat clearing, nasal congestion, or chronic rhinitis—though UACS may present without prominent nasal symptoms 1, 2
• When upper-airway symptoms are prominent, add topical intranasal corticosteroid therapy 2
• Maintain treatment for 4–6 weeks before deeming it ineffective 1, 2

Step 2: Asthma (Including Cough-Variant Asthma)

Asthma accounts for 15–41% of chronic cough and may present with cough as the sole manifestation—normal spirometry does not exclude asthma. 3, 1, 2

• Perform methacholine bronchial provocation testing in patients with normal spirometry and no clinically obvious etiology 3, 2
• Initiate inhaled corticosteroids according to national asthma guidelines 2, 6
• A 2-week trial of oral prednisone 30–40 mg daily differentiates eosinophilic airway inflammation; lack of improvement makes eosinophilic mechanisms unlikely 2, 5
• For refractory cough-variant asthma, add leukotriene-receptor antagonists rather than long-acting β-agonists 2
• Suspect asthma when cough worsens at night, with cold air exposure, or with exercise 1

Step 3: Gastroesophageal Reflux Disease (GERD)

GERD contributes to 5–85% of chronic cough and frequently occurs without typical gastrointestinal symptoms (heartburn, regurgitation). 3, 1, 2

Acid suppression alone is no longer recommended as sole therapy—comprehensive GERD management is required. 1, 2

• Initiate intensive acid suppression with omeprazole 20–40 mg twice daily before meals for ≥8 weeks 2, 5
• Add alginate therapy to the proton-pump inhibitor regimen 2
• Implement dietary and lifestyle modifications, including removal of medications that aggravate reflux (bisphosphonates, nitrates, calcium-channel blockers, theophylline, progesterone) 2
• Add prokinetic agent (metoclopramide 10 mg three times daily) if response to PPIs is inadequate 2
• Clinical response may require 2–12 weeks; failure to allow adequate trial duration is a common pitfall 1, 2
• Consider antireflux surgery in carefully selected patients after comprehensive evaluation including 24-hour pH monitoring, esophageal manometry, and documented PPI trial failure 2

Step 4: Nonasthmatic Eosinophilic Bronchitis (NAEB)

NAEB accounts for 6–17% of chronic cough and is characterized by eosinophilic airway inflammation without airway hyperresponsiveness or variable airflow obstruction. 3, 1, 2

• Treat with inhaled corticosteroids, which are effective in reducing cough severity 2, 5
• Patients have normal spirometry and negative methacholine challenge, distinguishing NAEB from asthma 2

Advanced Evaluation for Refractory Cough

When empiric therapies fail after 8 weeks:

• Obtain high-resolution CT of the chest to evaluate for bronchiectasis, interstitial lung disease, or occult masses 3, 1
• Consider bronchoscopy to assess for endobronchial lesions, sarcoidosis, eosinophilic bronchitis, or occult infection 3, 1
• Refer to a specialist cough clinic for comprehensive multidisciplinary evaluation 1, 2

Management of Refractory Chronic Cough

After excluding treatable causes:

• Consider cough hypersensitivity syndrome as the underlying mechanism 1, 4
• Trial gabapentin starting at 300 mg once daily, escalating to maximum 1,800 mg daily in divided doses 1, 5, 4
• Alternative options include pregabalin or low-dose morphine 5, 4
• Multimodality speech pathology therapy is an evidence-based non-pharmacologic approach 1, 4

Critical Management Principles

• Retain partially effective therapies and employ additive treatment strategies because multiple etiologies coexist in up to 67% of patients 1, 2
• Schedule follow-up within 4–6 weeks to reassess cough severity using validated instruments and verify treatment adherence 1, 2, 6
• Formally quantify treatment effects at each visit using cough-severity measures 3, 1
• Assess occupational and environmental exposures systematically in all patients 3, 1, 2

Common Pitfalls to Avoid

• Assuming a single etiology when 25–67% of patients have multiple simultaneous causes requiring combination therapy 1, 2, 6
• Failing to discontinue ACE inhibitors before pursuing extensive workup 1, 2
• Using acid suppression alone for GERD-related cough without comprehensive lifestyle modifications and adequate trial duration 1, 2
• Abandoning therapeutic trials prematurely—maintain each treatment for 4–6 weeks before declaring failure 1, 2
• Neglecting to quantify cough severity objectively, which prevents accurate assessment of treatment response 3, 1