What is the evaluation and treatment approach for a persistent cough lasting 1 month?

Evaluation and Management of 1-Month Cough

A 1-month cough is classified as subacute (3-8 weeks duration) and should be evaluated first to determine if it is postinfectious or non-infectious, then managed with sequential empiric therapy targeting the most common causes. 1

Initial Critical Actions

• Discontinue ACE inhibitors immediately if the patient is taking one, as this is a common reversible cause that resolves within days to 2 weeks (median 26 days) 1, 2
• Counsel smokers on cessation, as 90-94% experience cough resolution within the first year of quitting, often within 4 weeks 1, 2
• Obtain a chest radiograph to rule out pneumonia, structural abnormalities, masses, interstitial disease, or congestive heart failure 1, 2
• Assess for red flag symptoms including fever, night sweats, weight loss, hemoptysis, or recurrent pneumonia that would require urgent evaluation 1, 2

Subacute Cough Classification (3-8 Weeks)

Determine if Postinfectious or Non-Infectious

For postinfectious cough (began with acute respiratory infection 3-8 weeks ago):

• First-line: Inhaled ipratropium for symptomatic relief 2
• Second-line: Inhaled corticosteroids if ipratropium fails 2
• Consider short course of oral prednisone for severe paroxysms after ruling out other causes 2
• Evaluate for upper airway cough syndrome (UACS), transient bronchial hyperresponsiveness, asthma, or pertussis as potential causes 1

For non-infectious subacute cough, manage the same way as chronic cough using the sequential algorithm below 3, 1

Sequential and Additive Treatment Algorithm

The American College of Chest Physicians emphasizes that multiple causes frequently coexist, requiring sequential AND additive therapy rather than treating only one condition 3, 1

Step 1: Upper Airway Cough Syndrome (UACS)

• Initiate first-generation antihistamine/decongestant combination for 1-2 weeks 1, 4, 2
• Add topical nasal corticosteroid if prominent upper airway symptoms (nasal discharge, throat clearing, postnasal drip sensation, nasal congestion, or rhinorrhea) are present 1, 2
• Do not stop this therapy even if moving to Step 2, as multiple causes often coexist 3, 1

Step 2: Asthma Evaluation (If Cough Persists After 1-2 Weeks)

• Perform spirometry to assess for reversible airflow obstruction 1, 2
• If spirometry shows reversible obstruction: Treat with inhaled corticosteroids combined with long-acting β-agonists 1, 4
• If spirometry is normal: Consider bronchoprovocation challenge or proceed with empiric trial of inhaled corticosteroids and bronchodilators 3, 1, 2
• Suspect asthma when cough worsens at night, with cold air exposure, or with exercise 2
• Response to bronchodilators may occur within 1 week, but complete resolution can take up to 8 weeks 2
• Continue UACS treatment while adding asthma therapy 3, 1

Step 3: Non-Asthmatic Eosinophilic Bronchitis (NAEB)

• Perform induced sputum test for eosinophils if available 3, 1
• If testing unavailable: Empiric trial of inhaled corticosteroids 3, 1, 4
• Continue both UACS and asthma treatments while adding NAEB therapy 3, 1

Step 4: Gastroesophageal Reflux Disease (GERD)

• Initiate empiric treatment with proton pump inhibitors (PPIs) if cough persists after addressing UACS, asthma, and NAEB 3, 1, 4
• Add dietary modifications and lifestyle changes (avoid late meals, elevate head of bed, avoid trigger foods) 2
• Add prokinetic therapy if little or no response to PPI therapy 4
• Be patient: GERD therapy requires 2 weeks to several months for response, with some patients requiring 8-12 weeks before improvement 2
• Continue all previous therapies while adding GERD treatment 3, 1

Advanced Evaluation (If No Response After 4-6 Weeks)

• Pursue high-resolution CT scan to evaluate for bronchiectasis, interstitial lung disease, or occult masses 1, 2
• Consider 24-hour esophageal pH monitoring if GERD empiric therapy failed 2
• Consider bronchoscopy to evaluate for endobronchial lesions, sarcoidosis, eosinophilic bronchitis, or occult infection 2
• Refer to a specialist cough clinic when diagnosis remains unclear 1, 4

Critical Pitfalls to Avoid

• Do not rely on cough characteristics alone (productive vs. dry, timing, quality), as they have little diagnostic value 1, 4
• Do not treat only one cause and stop—multiple factors contribute simultaneously in the majority of cases, requiring additive therapy 3, 1, 4
• Do not label as idiopathic until thorough assessment at a specialist clinic excludes uncommon causes 1
• Do not use routine cough suppressants when cough clearance is important for underlying conditions 1

Special Populations

• In immunocompromised patients: Use the same initial algorithm but expand the differential diagnosis based on immune defect type and severity 1
• In HIV patients with CD4+ <200 cells/μL: Suspect Pneumocystis pneumonia, tuberculosis, and opportunistic infections 1
• In high-prevalence areas: Obtain sputum smears, cultures for acid-fast bacilli, and chest radiograph to evaluate for tuberculosis 1