What is the best approach to manage an adult patient with a history of respiratory issues, presenting with chronic phlegm and occasional cough?

Management of Chronic Phlegm and Occasional Cough

Begin with a chest radiograph and spirometry with bronchodilator response as mandatory first-line investigations, then pursue empiric treatment targeting the three most common causes: upper airway cough syndrome (UACS), asthma, and gastroesophageal reflux disease (GERD), which account for 90% of chronic cough cases. 1, 2

Initial Mandatory Workup

All patients require:

• Chest radiograph to exclude malignancy, infection, structural abnormalities, and bronchiectasis 3, 1
• Spirometry with bronchodilator response to identify airflow obstruction and assess reversibility 3, 1
• Medication review to identify and discontinue ACE inhibitors if present, as these are a common reversible cause 1, 4

The chest radiograph is abnormal in 31% of patients with chronic cough and may provide a definitive diagnosis 3. However, normal spirometry does not exclude asthma, as cough-variant asthma commonly presents without airflow obstruction 3, 1.

Algorithmic Approach to Empiric Treatment

Step 1: Treat Upper Airway Cough Syndrome First

• Start with a first-generation antihistamine-decongestant combination as UACS is the most common single cause 1
• Allow at least 1-2 weeks for response 1
• UACS accounts for chronic cough even when physical examination and sinus imaging appear normal 5

Step 2: Assess for Asthma if UACS Treatment Fails

• Perform bronchial provocation testing (methacholine challenge) in patients with normal spirometry 1
• A negative methacholine challenge effectively excludes asthma 1
• If methacholine testing is unavailable, trial a 2-week course of oral corticosteroids (e.g., prednisolone) 3, 1
• Improvement with corticosteroids confirms eosinophilic airway inflammation 3, 1

Step 3: Empiric GERD Treatment

• Initiate intensive acid suppression therapy without diagnostic testing as the preferred initial approach 1
• Treatment requires at least 3 months for proper evaluation, as shorter trials are inadequate 1
• GERD commonly causes cough without typical gastrointestinal symptoms 1
• Consider 24-hour esophageal pH monitoring only if empiric treatment fails 1

Critical Recognition: Multifactorial Cough

Chronic cough is frequently caused by two or all three common diagnoses (UACS, asthma, GERD) simultaneously, and cough will not resolve until all contributing factors are treated. 1, 6 This accounts for 59% of chronic cough cases 6.

Common Pitfalls to Avoid

• Do not rely solely on spirometry to diagnose asthma, as cough-variant asthma presents with normal spirometry in the majority of cases 3, 1
• Do not use single peak expiratory flow (PEF) measurements for diagnosis, as they are less accurate than FEV1 3
• Do not overlook GERD even without gastrointestinal symptoms, as reflux-associated cough is often silent 1
• Do not terminate GERD treatment prematurely—inadequate trial periods (less than 3 months) lead to false-negative assessments 1
• Avoid cough suppressants, expectorants, and mucolytics as initial therapy, as they have no clear benefit and may impair secretion clearance 7

When to Pursue Advanced Investigation

Consider further workup if:

• Patient is immunocompromised or from tuberculosis-endemic area 1
• Red flag symptoms present: hemoptysis, dyspnea, prolonged fever, weight loss, or recurrent pneumonia 8, 2
• Symptoms persist despite optimal treatment of common causes 1, 2

Advanced investigations include:

• High-resolution CT chest to evaluate for bronchiectasis, interstitial lung disease, or occult malignancy 1
• Bronchoscopy if structural abnormalities or endobronchial lesions suspected 1

Specialist Referral

Chronic cough should only be labeled as idiopathic after thorough assessment at a specialist cough clinic, as refractory cases may represent cough hypersensitivity syndrome treatable with gabapentin or pregabalin 1, 2

Symptomatic Treatment Considerations

While investigating and treating underlying causes:

• Dextromethorphan 60 mg provides maximum cough suppression, superior to standard 15-30 mg doses 8
• Benzonatate 100-200 mg three to four times daily acts peripherally to reduce cough reflex 8
• Honey with lemon may be effective for benign viral cough 8

However, symptomatic treatment should never replace investigation of the underlying cause, particularly in older adults where serious pathology must be excluded 8.