Professional and Linguistic Assessments Board (PLAB) Practice Exam

What should be done if pleural LDH to serum LDH ratio is greater than 0.6 in a pleural effusion?

1. Confirmed as transudative.

2. Considered exudative.

3. Requires immediate drainage.

4. Should be monitored without intervention.

The correct answer is: Considered exudative.

When the pleural LDH to serum LDH ratio is greater than 0.6, the pleural effusion is categorized as exudative. This classification is essential because it typically suggests a pathological process is present in the pleura. Exudative effusions may result from conditions such as infections (like pneumonia), malignancies, or inflammatory diseases, wherein the pleural space becomes inflamed or compromised, leading to the leakage of proteins and LDH into the pleural fluid. The distinction between transudative and exudative pleural effusions is crucial for diagnosis and management. Transudative effusions usually result from systemic conditions leading to imbalances in hydrostatic or oncotic pressures, such as heart failure or cirrhosis, and usually have a lower LDH level. In contrast, higher levels of LDH, as indicated by the ratio exceeding 0.6, reflect a more complex pathology that may require further investigation and potentially therapeutic interventions. For this reason, if the pleural LDH to serum LDH ratio is greater than 0.6, the effusion should be considered exudative, prompting further diagnostic workup and appropriate management based on the underlying cause.