What are the typical features of the synovial fluid in Rheumatoid Arthritis?
The synovial fluid is inflammatory, with white blood cell (WBC) counts typically between 5000 and 50,000/mm 3 . Rarely, synovial fluid WBC count can exceed 100,000/mm 3 (pseudoseptic) but infection must always be ruled out. Generally the differential shows a predominance (>50%) of PMNs. The protein level is elevated, and the glucose level may be lower than serum values (40%–60% of serum glucose). There are no crystals in the fluid, and cultures are negative. Unfortunately, there are no specific findings in the synovial fluid that allow a definitive diagnosis of RA.