Synovial fluid analysis for diagnosis of intercritical gout

Background: The diagnosis of gout in the intercritical phase can be difficu lt. Objective: To determine whether synovial fluid analysis allows the diagnosi s of intercritical gout. Design: Cross-sectional study. Setting: Outpatient rheumatology clinics. Patients: 101 patients with gout. Intervention: Arthrocentesis of 80 knees and 21 first metatarsophalangeal j oints teach joint from a different patient) that had been inflamed but were currently asymptomatic. Measurements: Frequency with which arthrocentesis yielded synovial fluid; p resence of monosodium urate crystals in the synovial fluid sample; and, for synovial fluid with crystals, the number of microscope fields that had to be scanned before crystals were found. Results: Synovial fluid was obtained from 91 of 101 joints. The fluid from all 43 patients not receiving hypouricemic agents contained monosodium urat e crystals. These crystals were found in the synovial fluid of only 34 of 4 8 patients receiving hypouricemic agents. In 90% of the synovial fluid samp les that contained crystals, crystals were seen in the first five microscop e fields examined. Conclusions: Arthrocentesis of asymptomatic knees and first metatarsophalan geal joints and synovial fluid analysis are simple procedures that facilita te the diagnosis of gout during intercritical periods.