Arab Board IM Final Written

Practice session

A 54-year-old man undergoes diagnostic thoracentesis for a moderate right-sided pleural effusion. Laboratory evaluation of the pleural fluid and simultaneous serum samples reveals: Pleural fluid protein: 4.2 g/dL (Serum protein: 6.4 g/dL), Pleural fluid LDH: 280 U/L (Serum LDH: 320 U/L; upper limit of normal serum LDH is 200 U/L). According to Light's criteria, which of the following best characterizes this pleural effusion?

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