Septic Arthritis in Immunosuppressed Patients: Do Laboratory Values Help?

UNLABELLED: 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.