EVALUATION OF ACCURACY OF SYNOVIAL FLUID LEUKOCYTE ESTERASE IN DIAGNOSING SEPTIC ARTHRITIS

Abstract

Background: Septic arthritis is an orthopedic emergency requiring rapid diagnosis to prevent irreversible joint damage. Synovial fluid leukocyte esterase (LE) dipstick testing is a rapid bedside alternative to conventional culture. Objective: To evaluate the diagnostic accuracy of synovial fluid leukocyte esterase for diagnosing bacterial septic arthritis and compare its performance with synovial fluid culture. Materials and Methods: This hospital-based cross-sectional observational study included 65 adults with clinically suspected bacterial septic arthritis. Synovial fluid samples underwent LE dipstick testing and microbiological culture. Dipstick readings of 2+ and 3+ were considered positive. Diagnostic performance was assessed using sensitivity, specificity, predictive values, accuracy, odds ratio, and ROC analysis. Results: Of the 65 patients, 40 (61.5%) were diagnosed with bacterial septic arthritis. Leukocyte esterase positivity was observed in 52 (80.0%) patients and showed a significant association with bacterial septic arthritis (95.0% vs. 56.0%; p=0.000225). Positive LE was identified as the strongest independent predictor of septic arthritis (OR=14.9, 95% CI: 2.8–78.5; p=0.0002). Using synovial fluid culture as the reference standard, LE demonstrated a sensitivity of 94.7%, specificity of 26.1%, PPV of 34.6%, NPV of 92.3%, and accuracy of 46.2%. Against the diagnosis of bacterial septic arthritis, sensitivity, specificity, PPV, NPV, and accuracy were 95.0%, 44.0%, 73.1%, 84.6%, and 75.4%, respectively. ROC analysis yielded an AUC of 0.78. Conclusion: Synovial fluid leukocyte esterase is a rapid, inexpensive, and highly sensitive bedside screening test that can support early diagnosis and timely management of bacterial septic arthritis while awaiting culture confirmation.