Pleural exudates are typically characterized by which laboratory pattern?

Pleural exudates are typically characterized by which laboratory pattern?

• A. Increased LDH in pleural fluid relative to serum
• B. Decreased LDH
• C. Normal LDH
• D. Decreased protein

Answer: (A)

Pleural exudates reflect inflammatory or malignant processes that increase capillary permeability, letting proteins and enzymes like LDH leak into the pleural space. A hallmark pattern is that LDH is higher in the pleural fluid than in the serum. This relative elevation is captured by Light’s criteria, which state that an exudate is indicated if the pleural fluid-to-serum LDH ratio exceeds 0.6, or if pleural fluid LDH is more than two-thirds the upper limit of normal for serum LDH. In contrast, transudates from systemic factors such as heart failure or hypoalbuminemia typically do not show this relative rise in pleural LDH. Therefore, increased LDH in pleural fluid relative to serum best identifies an exudate.

Pleural exudates reflect inflammatory or malignant processes that increase capillary permeability, letting proteins and enzymes like LDH leak into the pleural space. A hallmark pattern is that LDH is higher in the pleural fluid than in the serum. This relative elevation is captured by Light’s criteria, which state that an exudate is indicated if the pleural fluid-to-serum LDH ratio exceeds 0.6, or if pleural fluid LDH is more than two-thirds the upper limit of normal for serum LDH. In contrast, transudates from systemic factors such as heart failure or hypoalbuminemia typically do not show this relative rise in pleural LDH. Therefore, increased LDH in pleural fluid relative to serum best identifies an exudate.