What is the best approach to manage a nonproductive cough in an adult patient with a history of recurrent cough and no response to antibiotics, presenting with no other symptoms?

Management of Nonproductive Cough with No Other Symptoms

In an adult with recurrent nonproductive cough unresponsive to antibiotics and no other symptoms, pursue a systematic diagnostic approach prioritizing cough-variant asthma, upper airway cough syndrome, and gastroesophageal reflux disease, with empiric treatment trials guided by clinical suspicion when initial testing is nondiagnostic. 1

Initial Mandatory Evaluation

• Obtain chest radiograph and spirometry in all patients - these are mandatory baseline investigations to exclude structural lung disease and assess airway obstruction 1
• Perform detailed occupational and environmental exposure history, as irritant exposure is a common aggravating factor 1
• Review all medications, particularly ACE inhibitors - no patient with troublesome cough should continue ACE inhibitors 1
• Assess smoking status, as smoking is one of the commonest causes of persistent cough in a dose-related fashion 1

Most Common Etiologies to Consider

The three most common causes account for approximately 90% of chronic nonproductive cough cases 1, 2:

1. Cough-Variant Asthma (CVA)

• Asthma should always be considered as a potential etiology because it is a common condition commonly associated with cough 1
• CVA presents with isolated cough as the predominant or sole symptom, with physical examination and spirometry often entirely normal 1
• Perform methacholine inhalation challenge testing in patients without clinically obvious etiology who have normal spirometry - this demonstrates bronchial hyperresponsiveness 1
• The diagnosis is only confirmed after resolution of cough with antiasthmatic therapy 1
• If methacholine challenge testing cannot be performed, initiate empiric therapy with inhaled bronchodilators and inhaled corticosteroids 1
• Cough is unlikely to be due to eosinophilic airway inflammation if there is no response to a two-week oral steroid trial 1

2. Upper Airway Cough Syndrome (UACS)

• Previously termed postnasal drip syndrome, UACS is diagnosed by combination of symptoms, physical examination, and response to specific therapy 1
• For patients without apparent cause, initiate empiric trial with first-generation antihistamine/decongestant preparation before extensive workup 1
• If no response to first-generation antihistamine/decongestant, obtain sinus imaging - chronic sinusitis may be clinically silent with relatively or completely nonproductive cough 1
• In the presence of prominent upper airway symptoms, trial topical corticosteroid 1
• Newer generation nonsedating antihistamines are ineffective for cough reduction and should not be used 1

3. Gastroesophageal Reflux Disease (GORD)

• Failure to consider GORD is a common reason for treatment failure 1
• Reflux-associated cough may occur in the complete absence of gastrointestinal symptoms 1
• Initiate intensive acid suppression with proton pump inhibitors and alginates for a minimum of 3 months 1
• This prolonged trial is necessary as reflux cough may take months to respond 1

Algorithmic Treatment Approach

Step 1: If patient is smoking, mandate smoking cessation as first intervention 1

Step 2: Discontinue ACE inhibitors if present 1

Step 3: Based on clinical suspicion, initiate empiric trial in this order:

• If any suggestion of upper airway symptoms: first-generation antihistamine/decongestant 1
• If no upper airway features: inhaled bronchodilator plus inhaled corticosteroid for presumed CVA 1
• Consider concurrent GORD treatment with proton pump inhibitor, especially if multiple failed trials 1

Step 4: If no response after 2 weeks of corticosteroid therapy, CVA is effectively ruled out 1

Step 5: If initial empiric therapy fails and spirometry is normal, perform methacholine challenge testing 1

Step 6: If methacholine challenge is negative and upper airway treatment failed, initiate 3-month trial of intensive acid suppression for GORD 1

Advanced Diagnostic Testing

• Bronchial provocation testing should be performed in patients without clinically obvious etiology referred to respiratory physician with chronic cough and normal spirometry 1
• High-resolution computed tomography may be useful when other targeted investigations are normal 1
• Consider bronchoscopy only if foreign body inhalation is suspected 1

Critical Pitfalls to Avoid

• Do not use antibiotics for nonproductive cough without evidence of bacterial infection - the patient's lack of response to antibiotics confirms this is not bacterial 1
• Do not assume single etiology - up to 25% of patients have dual causes contributing simultaneously 3
• Do not use newer nonsedating antihistamines - they are ineffective for cough 1
• Do not give up on GORD treatment prematurely - requires minimum 3 months of intensive therapy 1
• Do not prescribe inhaled corticosteroids if bronchial hyperresponsiveness testing is negative, as this will not help 4

Refractory Cases

• Chronic cough should only be considered idiopathic following thorough assessment at specialist cough clinic 1
• For unexplained chronic cough after negative evaluation, consider cough hypersensitivity syndrome 2
• Multimodality speech pathology therapy is the initial non-pharmacological approach for unexplained chronic cough 4
• Gabapentin may be considered, starting at 300 mg once daily and escalating to maximum 1,800 mg daily in divided doses, with reassessment of risk-benefit at 6 months 4

Treatment Effect Monitoring

• Treatment effects should be formally quantified using cough visual analogue scores or cough-specific quality of life questionnaires 1
• Reassess after each therapeutic trial with objective measurement 1
• The decrement in quality of life from chronic cough is comparable to severe COPD, justifying aggressive diagnostic and therapeutic approach 1