American Board of Internal Medicine (ABIM) Certification Practice Exam

What is the serum effusion protein gradient that indicates a transudate in patients being diuresed?

1. Less than 2.5

2. Between 2.5 and 3.0

3. Greater than 3.1

4. Exactly 3.0

The correct answer is: Greater than 3.1

A serum effusion protein gradient of greater than 3.1 mg/dL is indicative of a transudate condition in patients, particularly those being diuresed. This measurement is part of the Light's criteria, which are used to classify pleural effusions based on the relationship between the proteins in the serum and the effusion fluid. When the gradient exceeds this threshold, it essentially means that the protein concentration in the effusion is significantly lower than that in the serum, which is characteristic of transudative effusions often seen in conditions like congestive heart failure or cirrhosis. This distinction is important in clinical practice as it can help guide the further evaluation and management of the patient. Furthermore, the presence of a transudate typically suggests that the underlying issue is related to a systemic condition rather than a local inflammatory process, which would often lead to an exudative effusion with a different protein gradient profile.