If only suspect infection / empyema don't only order gram stain and culture

• Cell count with diff (CBCD)
• Total Protein
• LDH
• Gram stain and Culture

Otherwise...

• Routine
• Cell count with differential
• Glucose
• Cytology
• Gram stain and Culture
• Selective Testing: Order if High Clinical Suspicion for Diagnosis
• ADA (adenosine deaminage) if considering TB
• Amylase if considering pancreatitis, esophageal rupture (malignancy, CABG, ruptured ectopic, TB)
• Triglycerides if considering chylothorax, intrathoracic TPN infusion
• Creatinine (with serum measurement) if considering Urinothorax
• Albumin (with serum measurement) if considering CHF after diuretics (exudative effusions)
• Interferon Gamma if considering TB (malignancy, empyema)
• PCR if considering TB
• pH if considering complicated parapneumonic effusion
• I am not sure about
• Bilirubin- only if ascites also present
• Total Protein
• LDH
• TB smear and culture
• Lactate

TABLE 9–3 -- Exudates: Evaluation of the Undiagnosed Exudative Effusion Roberts: Clinical Procedures in Emergency Medicine, 5th ed.
Read the table for the findings to diagnose the different conditions.