American Board of Internal Medicine (ABIM) Certification Practice Exam

What is considered a normal leukocyte count in joint fluid analysis?

1. Less than 200/µL

2. 200/µL to 2000/µL

3. Greater than 2000/µL

4. Greater than 50,000/µL

The correct answer is: Less than 200/µL

A normal leukocyte count in joint fluid analysis is defined as less than 200 cells per microliter (µL). This threshold is used to differentiate between normal and inflammatory or infectious processes in the joint. When the leukocyte count is below this level, it generally indicates that there is no significant inflammation or infection present in the joint fluid. In contrast, higher leukocyte counts suggest various pathological conditions: counts ranging from 200 to 2000/µL often indicate non-infectious inflammatory processes, while counts greater than 2000/µL are usually associated with infectious or some other severe inflammatory conditions. Counts that exceed 50,000/µL are indicative of septic arthritis, which is a medical emergency. Understanding the normal range of leukocyte counts in joint fluid is essential for clinicians to make accurate diagnoses and, subsequently, manage joint-related disorders effectively.