What diagnostic work‑up and initial management are recommended for a patient with a non‑acute cough that has been waxing and waning for weeks, accompanied by post‑tussive nausea/vomiting and night sweats?

Diagnostic Work-Up and Management for Non-Acute Cough with Post-Tussive Vomiting and Night Sweats

This patient requires immediate evaluation for pertussis (whooping cough) and tuberculosis, as the combination of prolonged cough with post-tussive vomiting and night sweats strongly suggests these potentially serious infections.

Priority Diagnostic Considerations

Pertussis (Bordetella pertussis)

The clinical presentation is highly suggestive of pertussis. When a patient has cough lasting ≥2 weeks accompanied by paroxysms of coughing and post-tussive vomiting, the diagnosis of Bordetella pertussis infection should be made unless another diagnosis is proven 1, 2, 1. Post-tussive vomiting has moderate sensitivity (32.5%) but high specificity (77.7%) for pertussis in adults 3. Night sweats have been documented as a symptom of pertussis in adults (14% of cases) 4.

Tuberculosis

Night sweats combined with prolonged cough raises significant concern for pulmonary TB. The presence of cough with night sweats increases the likelihood of TB, particularly in at-risk populations 5. This must be ruled out given the serious public health implications and mortality risk.

Immediate Diagnostic Testing

For Pertussis:

• Nasopharyngeal aspirate or Dacron swab for culture - this is the only certain way to make the diagnosis 1, 2
• Paired acute and convalescent sera for IgG or IgA antibodies to pertussis toxin (PT) or filamentous hemagglutinin (FHA) - a fourfold increase confirms recent infection 1, 2
• PCR testing is available but not recommended as routine due to lack of validated techniques 1, 2

For Tuberculosis:

• Chest radiograph - mandatory initial test 5
• Sputum for acid-fast bacilli (AFB) smear and culture - three samples
• XpertMTB/RIF testing if available (preferred over sputum microscopy alone) 5
• Consider HIV testing given the TB risk profile 5

Additional Initial Work-Up:

• Complete blood count with differential
• Chest radiograph (serves dual purpose for TB and other pathology)
• Spirometry and exhaled nitric oxide 6
• Blood eosinophil count 6

Immediate Management

If Pertussis is Confirmed or Highly Suspected:

Initiate macrolide antibiotic immediately and isolate the patient for 5 days from treatment start 1, 2. Early treatment within the first few weeks diminishes coughing paroxysms and prevents disease spread. Treatment options include:

• Azithromycin (preferred)
• Clarithromycin
• Erythromycin

Critical caveat: Treatment beyond the first few weeks of illness is unlikely to alter the clinical course but should still be offered to prevent transmission 1, 2.

Do NOT use long-acting β-agonists, antihistamines, corticosteroids, or pertussis immunoglobulin - there is no evidence of benefit 1, 2.

If TB is Confirmed:

Initiate standard four-drug anti-tuberculous therapy per local protocols and ensure appropriate isolation and contact tracing 5.

Alternative Diagnoses if Pertussis and TB are Excluded

If both pertussis and TB are ruled out and cough persists beyond 8 weeks, consider these diagnoses in order of likelihood 1:

1. Upper Airway Cough Syndrome (UACS) - formerly postnasal drip
2. Asthma/Cough-variant asthma
3. Gastroesophageal reflux disease (GERD)
4. Nonasthmatic eosinophilic bronchitis

Empiric Treatment Approach (if infectious causes excluded):

For postinfectious cough (3-8 weeks duration) 1, 2:

1. First-line: Inhaled ipratropium bromide (fair evidence, grade B)
2. Second-line: Inhaled corticosteroids if quality of life is affected and ipratropium fails
3. For severe paroxysms: Prednisone 30-40 mg daily for a short course after ruling out UACS, asthma, and GERD
4. Last resort: Central-acting antitussives (codeine or dextromethorphan)

Important: Antibiotics have NO role in postinfectious cough unless bacterial sinusitis or early pertussis is present 1, 2.

Critical Red Flags

• Hemoptysis - requires immediate bronchoscopy evaluation
• Significant weight loss - increases TB likelihood
• Fever - absence of fever is common in pertussis (sensitivity 81.8%) but presence suggests alternative diagnosis 3
• Immunocompromised state - dramatically increases TB risk

Common Pitfalls to Avoid

1. Delaying pertussis testing because the patient lacks the classic "whoop" - whooping is rare in adults (only 8%) 4
2. Assuming post-tussive vomiting is always GERD - this is a hallmark of pertussis
3. Treating empirically without considering TB when night sweats are present
4. Using antibiotics for postinfectious cough - they provide no benefit unless bacterial infection is documented 1, 2
5. Waiting for culture results before treating pertussis - start macrolides immediately if clinical suspicion is high

Timeline Considerations

• If cough persists >8 weeks: Consider diagnoses other than postinfectious cough 1, 2
• Pertussis cough duration: Mean 54 days in adults, with 80% lasting ≥21 days 4
• Treatment window for pertussis: Most effective within first few weeks of illness 1, 2