Which synovial fluid leukocyte count is most suggestive of infectious (septic) arthritis?

Which synovial fluid leukocyte count is most suggestive of infectious (septic) arthritis?

• A. <2000
• B. 2-75,000
• C. 50-100,000
• D. 100,000 and above

Answer: (D)

High synovial fluid leukocyte counts indicate intense joint inflammation, and in septic arthritis this response is neutrophil-dominated. When the count reaches 100,000 cells per microliter or more, infection becomes much more likely than noninfectious inflammatory processes. Lower counts can occur with inflammatory or crystal-related arthritis, so they’re less specific for infection. Therefore, a synovial fluid leukocyte count of 100,000 and above is the best indicator of septic arthritis, though confirmation with Gram stain, culture, and urgent joint drainage with antibiotics is essential.

High synovial fluid leukocyte counts indicate intense joint inflammation, and in septic arthritis this response is neutrophil-dominated. When the count reaches 100,000 cells per microliter or more, infection becomes much more likely than noninfectious inflammatory processes. Lower counts can occur with inflammatory or crystal-related arthritis, so they’re less specific for infection. Therefore, a synovial fluid leukocyte count of 100,000 and above is the best indicator of septic arthritis, though confirmation with Gram stain, culture, and urgent joint drainage with antibiotics is essential.