American Board of Internal Medicine (ABIM) Certification Practice Exam

What is considered a normal synovial fluid leukocyte count?

1. 100/µL

2. 200/µL

3. 300/µL

4. 400/µL

The correct answer is: 200/µL

In the context of synovial fluid analysis, a normal leukocyte count is typically regarded to be under 200 cells/µL. This count is an important metric used to differentiate between various types of arthritis and joint conditions. When inflammation or infection is suspected, an elevated leukocyte count can indicate disease processes such as infectious arthritis, inflammatory arthritis, or other connective tissue disorders. While the leukocyte counts mentioned in the choices are all above the normal threshold, the selected value is often aligned with some interpretations of a borderline area where mild inflammation may begin to be considered. However, it’s crucial to recognize that values close to that number still require contextual interpretation based on the patient's clinical picture and the presence of other symptoms. In summary, a normal synovial fluid leukocyte count is generally accepted to be lower than 200 cells/µL, and values above this threshold are often indicative of various conditions that could merit further clinical investigation.