Exudative pleural effusion workup — Light's criteria and when to do thoracoscopy?

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This is a classic TB pleural effusion presentation. Here's the systematic approach: **Light's Criteria Confirmation:** This is an exudate because: - Pleural LDH/Serum LDH = 280/190 = 1.47 (>0.6) ✓ - Pleural protein/Serum protein = 4.2/6.5 = 0.65 (>0.5) ✓ **ADA (Adenosine Deaminase) Interpretation:** - ADA >40 U/L in lymphocytic exudate = TB pleural effusion with sensitivity ~92%, specificity ~90% in high-prevalence countries (India, etc.) - ADA 32 U/L = borderline (normal usually <26; TB usually >40) - However, lymphocyte-predominant exudate + high ADA in a high-prevalence country strongly suggests TB **Diagnostic Approach (ERS/BTS Guidelines):** **Do NOT start empirical anti-TB without confirmation** (risk of drug resistance selection + side effects). **Step 1:** Repeat sputum AFB x3 (concentrated cultures), NAAT (Xpert MTB/RIF) on pleural fluid. **Step 2:** Pleural fluid Mycobacterial culture (Lowenstein-Jensen + MGIT) — takes 4-6 weeks but gold standard. **Step 3:** Image-guided pleural biopsy (Abrams/CT-guided) — sensitivity 70-80% for TB, shows caseating granulomas. **Step 4:** Medical thoracoscopy (if above inconclusive) — gold standard for undiagnosed exudative pleural effusion. Sensitivity >90% for TB pleuritis. **For this patient (ADA 32 — borderline):** - Proceed with CT-guided pleural biopsy or thoracoscopy before starting anti-TB therapy. - Thoracoscopy preferred: diagnostic yield >90%, therapeutic drainage in same procedure, can take multiple biopsies under direct vision. **Anti-TB therapy initiation:** Only after histological/microbiological confirmation unless clinical deterioration with high pre-test probability.