American Board of Internal Medicine (ABIM) Certification Practice Exam

What synovial fluid leukocyte count range is associated with noninflammatory conditions?

1. Less than 200/µL

2. Between 200/µL and 2000/µL

3. Between 2000/µL and 5000/µL

4. Greater than 5000/µL

The correct answer is: Between 200/µL and 2000/µL

The range associated with noninflammatory conditions in synovial fluid leukocyte count is less than 200/µL. This level of leukocytes indicates a normal state of the synovial fluid characterized by little to no inflammation. Counts below this threshold typically signify conditions such as osteoarthritis or normal joint homeostasis, where the synovial fluid remains clear and viscid, reflecting negligible immune activity. In contrast, a leukocyte count between 200/µL and 2000/µL typically indicates inflammatory conditions, such as rheumatoid arthritis or other inflammatory arthritides, where there is an elevated immune response and increased leukocyte presence in the synovial fluid. A leukocyte count higher than 2000/µL further suggests significant inflammation or infection, often pointing to conditions such as septic arthritis or crystal-induced arthropathies. Counts exceeding 5000/µL are particularly characteristic of acute inflammatory processes or infections. Therefore, the correct interpretation of synovial fluid leukocyte counts is critical for diagnosing the underlying cause of joint symptoms and guiding appropriate management.