Effects of immunocompromised status on diagnostic criteria in septic arthritis

Septic arthritis is an orthopaedic emergency, with permanent cartilage damage possible within hours of the onset of symptoms. Diagnostic criteria for septic arthritis in immunocompetent patients are well established, however, there is a paucity of literature evaluating diagnostic criteria in immunocompromised patients. The purpose of this retrospective case-control study was to evaluate the laboratory and clinical information of immunocompromised patients with septic arthritis and compare them to immunocompetent patients with septic arthritis to enable physicians to diagnose septic arthritis more accurately in this population.

All patients at our institution, a level I trauma center, with a clinical diagnosis of septic arthritis between January 1, 2006 and November 1, 2021 were identified and reviewed retrospectively. Patients 18 years old or older were screened for immunocompromised status and those meeting criteria were included for review. The control cohort was matched by the joint affected and age. Data were analyzed using the Shapiro-Wilk test, Turkey's test, Mann-Whitney U test, independent sample t-test, and chi-square analysis. A p-value of <0.05 was considered significant.

A total of 36 patients with positive joint aspirate cultures were compared (18 immunocompetent and 18 immunocompromised). The immunocompromised group had a significantly longer length of hospital stay than the immunocompetent group (p = 0.044). There was no significant difference in erythrocyte sedimentation rate (ESR) (p = 0.852), peripheral white blood cell count (pWBC) (p = 0.696), joint aspirate white blood cell count (aWBC) (p = 0.901), polymorphonuclear cell percentage (PMN%) (p = 0.325), or total operations performed per patient (p = 0.365).

At our institution, immunocompromised patients with septic arthritis did not have significantly different diagnostic laboratory values when compared to immunocompetent patients. This suggests that immunocompromised patients with suspicion of septic arthritis can be assessed with similar diagnostic criteria as immunocompetent individuals; however, a larger cohort study is needed to assess the difference more precisely in laboratory values.