A 32-year-old man from Delhi presents with a 3-week history of cough, fever, and night sweats. Chest X-ray shows cavitary lesions in the right upper lobe. Sputum smear microscopy is positive for acid-fast bacilli (AFB). He has no known comorbidities and denies HIV risk factors. What is the most appropriate next step in management?

Explanation

## Clinical Context This is a case of presumed pulmonary tuberculosis with sputum smear-positive status (AFB-positive), which is diagnostic and highly infectious. The patient requires prompt initiation of anti-TB therapy, but baseline investigations are essential before starting treatment. ## Why HIV Testing and LFTs Before Therapy? **Key Point:** HIV status determination is mandatory in all TB patients because: - It affects treatment regimen duration and composition - CD4 count guides timing of antiretroviral therapy (ART) initiation relative to TB therapy - TB-HIV coinfection requires modified dosing and closer monitoring **High-Yield:** Baseline liver function tests (LFTs) are essential because: - Isoniazid, rifampicin, and pyrazinamide are hepatotoxic - Pre-existing hepatic dysfunction alters drug metabolism and increases toxicity risk - Baseline values allow detection of drug-induced hepatotoxicity during treatment ## Treatment Initiation Timeline | Investigation | Timing | Rationale | |---|---|---| | HIV test | Before or at start of TB therapy | Determines ART timing and TB regimen | | LFTs, renal function | Before therapy start | Baseline for monitoring toxicity | | Sputum smear | Already done (positive) | Confirms diagnosis; no need to delay | | Culture & DST | Parallel to therapy initiation | Results guide later regimen adjustments if needed | **Clinical Pearl:** In smear-positive TB with typical clinical and radiological features, treatment should NOT be delayed awaiting culture/DST results (which take 2–8 weeks). Culture and DST are sent in parallel and used to modify therapy if drug resistance is detected. ## Why Not the Other Options? **Option 0 (Start HRZE immediately without baseline tests):** While treatment should not be delayed in smear-positive TB, omitting baseline HIV and LFT assessment is unsafe. HIV status is critical for regimen planning, and baseline LFTs are essential for monitoring. **Option 2 (Wait for culture and DST):** Culture takes 2–8 weeks to result. Delaying treatment initiation in a smear-positive, symptomatic patient with cavitary disease increases transmission risk, disease progression, and mortality. Culture/DST are obtained in parallel with therapy start. **Option 3 (Bronchoscopy/BAL):** Invasive procedures are not indicated in smear-positive TB with typical presentation. Sputum smear microscopy is diagnostic; BAL is reserved for smear-negative cases with high clinical suspicion or immunocompromised patients. [cite:Harrison 21e Ch 205]