In a pleural effusion, which set of Light's criteria identifies a transudate correctly?
- A Pleural protein/serum protein > 0.5 AND pleural LDH/serum LDH > 0.6
- B Pleural protein/serum protein < 0.5 AND pleural LDH/serum LDH < 0.6 AND pleural LDH < 2/3 upper limit of normal ✓
- C Pleural LDH > 200 IU/L with pleural protein > 3 g/dL
- D Pleural glucose < 60 mg/dL with pH < 7.2
Correct answer: B. Pleural protein/serum protein < 0.5 AND pleural LDH/serum LDH < 0.6 AND pleural LDH < 2/3 upper limit of normal
Explanation
Light's criteria classify a pleural effusion as a transudate if ALL three criteria are absent: pleural protein/serum protein <0.5, pleural LDH/serum LDH <0.6, AND pleural LDH < 2/3 the upper limit of normal serum LDH. An exudate meets ANY one criterion. The criteria listed in option B correctly define a transudate. Low glucose and pH suggest complicated parapneumonic effusion or empyema, which is an exudate.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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