Which laboratory findings are typical in OA?

Which laboratory findings are typical in OA?

• A. ESR less than 40
• B. RF less than 1:40
• C. Synovial fluid: Clear with WBC less than 2000
• D. All of the above

Answer: (D)

Osteoarthritis is a noninflammatory form of arthritis, so lab tests typically do not show strong inflammatory changes. The inflammatory marker ESR is usually normal or only mildly elevated in OA, and in practice many patients have an ESR well below 40. Rheumatoid factor is typically negative in OA, meaning RF levels are not raised. When synovial fluid is analyzed from an OA-related effusion, it looks noninflammatory—clear appearance with a low white blood cell count, usually under 2000 cells per microliter. Because each of these findings aligns with the noninflammatory nature of OA, the combination of normal-to-mild ESR, negative RF, and clear synovial fluid with low WBC best fits osteoarthritis.

Osteoarthritis is a noninflammatory form of arthritis, so lab tests typically do not show strong inflammatory changes. The inflammatory marker ESR is usually normal or only mildly elevated in OA, and in practice many patients have an ESR well below 40. Rheumatoid factor is typically negative in OA, meaning RF levels are not raised. When synovial fluid is analyzed from an OA-related effusion, it looks noninflammatory—clear appearance with a low white blood cell count, usually under 2000 cells per microliter. Because each of these findings aligns with the noninflammatory nature of OA, the combination of normal-to-mild ESR, negative RF, and clear synovial fluid with low WBC best fits osteoarthritis.