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.
Copyright © 2020 The Authors. Published by Wolters Kluwer Health, Inc. on behalf of the American Academy of Orthopaedic Surgeons.