Professional and Linguistic Assessments Board (PLAB) Practice Exam

What does Light's criteria indicate about pleural effusions?

1. They are always transudative.

2. They are likely exudative if at least one specific condition exists.

3. They require surgical intervention.

4. They indicate a bacterial infection.

The correct answer is: They are likely exudative if at least one specific condition exists.

Light's criteria are a set of criteria used to differentiate between transudative and exudative pleural effusions based on the analysis of pleural fluid. According to Light's criteria, a pleural effusion is categorized as exudative if at least one of the following conditions is met: 1. The ratio of pleural fluid protein to serum protein is greater than 0.5. 2. The ratio of pleural fluid lactate dehydrogenase (LDH) to serum LDH is greater than 0.6. 3. The pleural fluid LDH is greater than two-thirds of the upper limit of normal for serum LDH. If one or more of these criteria are met, it suggests that the effusion is likely due to some pathological process or disease, such as malignancy, infection, or inflammation, rather than just a simple transudate typically seen with conditions like heart failure or cirrhosis. This reasoning implies that the understanding of Light's criteria is crucial for clinicians when evaluating pleural effusions and making decisions about further management or treatment. Options indicating that pleural effusions are always transudative, require surgical interventions, or point exclusively to bacterial infections are overly simplistic and don't align with