What investigations should be sent for a patient with chronic cough and consolidation?

Investigations for Admitted Patient with Chronic Cough and Consolidation

For an admitted patient with chronic cough and consolidation on imaging, you must immediately send sputum for routine bacterial culture, acid-fast bacilli (AFB) smear and culture, and obtain CT chest imaging to characterize the consolidation and evaluate for underlying structural abnormalities like bronchiectasis or malignancy. 1, 2

Mandatory Initial Investigations

Microbiological Studies

• Sputum culture for routine bacteria and mycobacteria (AFB) - The presence of consolidation significantly increases the likelihood of infectious etiology including tuberculosis, particularly in endemic areas or patients with risk factors 2, 3
• Send three separate sputum samples for AFB smear and culture if TB is suspected based on clinical features (weight loss, night sweats, endemic area, prior TB history) 3, 4
• Consider fungal cultures if immunocompromised or specific risk factors present 2

Advanced Imaging

• High-resolution CT (HRCT) chest is essential when consolidation is present, as it will:
  • Characterize the consolidation pattern and extent 2
  • Identify bronchiectasis (missed in up to 34% of chest X-rays) 2
  • Detect interstitial lung disease, mediastinal lymphadenopathy, or masses 2
  • Guide need for bronchoscopy 2

Baseline Laboratory Tests

• Complete blood count to assess for eosinophilia (ABPA), leukocytosis (infection), or systemic disease 2, 1
• Serum immunoglobulins (IgG, IgA, IgM) to exclude immunodeficiency, particularly if recurrent infections 2
• Total IgE and Aspergillus-specific IgE to investigate for allergic bronchopulmonary aspergillosis (ABPA) 2

Pulmonary Function and Airway Assessment

Spirometry and Bronchial Testing

• Spirometry with bronchodilator response once acute infection treated - essential to identify underlying asthma or COPD 1, 2
• Bronchial hyperresponsiveness testing if spirometry normal but asthma suspected (cough-variant asthma may have normal baseline spirometry) 2, 1
• Consider induced sputum for eosinophil count to diagnose eosinophilic bronchitis if available 2, 1

Bronchoscopy Indications

Bronchoscopy should be performed when: 2

• Consolidation persists despite appropriate antibiotic therapy
• Malignancy suspected (mass lesion, hemoptysis, smoking history, weight loss) 2
• Foreign body aspiration suspected 2
• Recurrent pneumonia in same location 2
• Atypical presentation or immunocompromised state 2

Bronchoscopy allows bronchoalveolar lavage for additional microbiological studies and cytology, and direct visualization for endobronchial lesions 2, 3

Additional Targeted Investigations

If Specific Clinical Features Present

• 24-hour esophageal pH monitoring or empiric PPI trial if GERD symptoms present (though GERD can cause cough without typical reflux symptoms) 1, 2
• Sinus imaging if upper airway symptoms suggest chronic rhinosinusitis 2, 1
• Autoimmune serologies (RF, anti-CCP, ANA) if systemic features suggest connective tissue disease with associated bronchiectasis 2

Medication Review

• Immediately discontinue ACE inhibitors if patient is taking them - this is a common reversible cause that must be addressed regardless of temporal relationship 2, 1
• Cough typically resolves within days to 4 weeks after stopping ACE inhibitor (median 26 days) 2

Critical Pitfalls to Avoid

• Do not delay TB investigation in patients from endemic areas, with constitutional symptoms, or prior TB history - send AFB studies immediately 3, 4
• Do not rely solely on chest X-ray - HRCT detects bronchiectasis and other pathology missed in 34-42% of cases with "normal" radiographs 2
• Do not assume consolidation equals simple pneumonia - persistent consolidation after appropriate antibiotics mandates bronchoscopy to exclude malignancy or foreign body 2, 4
• Do not overlook immunodeficiency - measure immunoglobulins in all patients with bronchiectasis or recurrent infections 2

When to Escalate Investigation

Proceed to more invasive testing (bronchoscopy, transbronchial biopsy, or surgical biopsy) if: 2

• Consolidation fails to resolve after 4-6 weeks of appropriate treatment
• Red flags present: hemoptysis, weight loss, smoking history, progressive dyspnea 2, 5
• Rapid clinical deterioration or declining lung function 2
• Multiple negative investigations but symptoms persist 2