Septic Arthritis in Immunosuppressed Patients: Do Laboratory Values Help?

Abstract

Introduction:Previous studies have recommended synovial fluid cell count thresholds of 50,000 cells/mm−3 to diagnose septic arthritis; however, data to support this are limited. It is also unknown if this value is valid in immunosuppressed patients.Methods:We retrospectively reviewed 33 immunosuppressed patients treated at our institution from 2008 to 2018. We compared culture-positive patients with culture-negative patients.Results:We found no statistically significant differences in synovial fluid cell count, percent synovial fluid neutrophils, erythrocyte sedimentation rate, or C-reactive protein between the groups (all P = 0.081). The median synovial fluid cell count in the culture-positive cohort was 29,000 cells/mm−3, with only 31.2% having >50,000 cells/mm−3.Conclusion:Traditional synovial fluid cell thresholds are not a reliable method of diagnosing septic arthritis in immunosuppressed patients.