Diagnostic Performance of the BioFire® Joint Infection Panel in Native Septic Arthritis and Periprosthetic Joint Infection: A Retrospective Diagnostic Accuracy Study

Objective: Rapid identification of causative microorganisms is essential in suspected native septic arthritis and periprosthetic joint infection. This study evaluated the diagnostic performance of the BioFire® Joint Infection Panel and assessed its agreement with conventional culture and systemic inflammatory biomarkers. Methods: Hospital records from January 2025 to April 2026 were retrospectively reviewed. Of 115 screened patients with suspected joint infection, nine were excluded because BioFire® testing had not been performed and only culture results were available. The final analysis included 106 synovial fluid samples. All samples were tested using conventional culture and the BioFire® Joint Infection Panel during the same clinical episode. Demographic data, infection category, localization, C-reactive protein, erythrocyte sedimentation rate, procalcitonin, and white blood cell count were recorded. Agreement was assessed using Cohen’s kappa, discordance using the McNemar test, and diagnostic performance using culture as the reference method. Results: Sixty-five samples (61.3%) were classified as suspected native septic arthritis and 41 (38.7%) as periprosthetic joint infection. BioFire® was positive in 22 samples (20.8%) and culture was positive in 32 (30.2%). Overall agreement was 86.8%, with substantial agreement according to Cohen’s kappa (0.656). Discordance was significant, predominantly due to culture-positive/BioFire®-negative samples (P = 0.013). BioFire® showed 62.5% sensitivity [95% confidence interval (CI): 43.7-78.9), 97.3% specificity (95% CI: 90.6-99.7), 90.9% positive predictive value, 85.7% negative predictive value, and 86.8% accuracy. C-reactive protein, procalcitonin, and white blood cell counts were significantly higher in patients with suspected native septic arthritis. Conclusion: The BioFire® Joint Infection Panel provides rapid and highly specific microbiological support in suspected joint infection. However, its moderate sensitivity and inability to detect off-panel organisms indicate that it should complement rather than replace conventional culture.