Septic Arthritis in Immunosuppressed Patients: Do Laboratory Values Help?

Bell, Jared; Rasmussen, Luke; Kumar, Arun; Heckman, Michael G; Lesser, Elizabeth R; Whalen, Joseph; Shi, Glenn G; Wilke, Benjamin K · J Am Acad Orthop Surg Glob Res Rev · 2020

retrospective_cohort · Level III

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Abstract

Previous studies have recommended synovial fluid cell count thresholds of 50,000 cells/mm<sup>-3</sup> to diagnose septic arthritis; however, data to support this are limited. It is also unknown if this value is valid in immunosuppressed patients. We retrospectively reviewed 33 immunosuppressed patients treated at our institution from 2008 to 2018. We compared culture-positive patients with culture-negative patients. 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 <i>P</i> = 0.081). The median synovial fluid cell count in the culture-positive cohort was 29,000 cells/mm<sup>-3</sup>, with only 31.2% having >50,000 cells/mm<sup>-3</sup>. Traditional synovial fluid cell thresholds are not a reliable method of diagnosing septic arthritis in immunosuppressed patients.

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