Omar_2014_J.Bone.Joint.Surg.Am_96_2032

BACKGROUND: Most currently used tools to diagnose septic arthritis are either not readily available or fail to provide real-time results. Reagent strip tests have identified infections in various body fluids. We hypothesized that combined leukocyte esterase and glucose strip tests can aid in diagnosing septic arthritis in native synovial fluid because (1) leukocyte esterase concentrations would be elevated at the infection site because of secretion by recruited neutrophils, and (2) glucose concentrations would be reduced because of bacterial metabolism.
METHODS: We prospectively investigated synovial fluid from consecutive patients with an atraumatic joint effusion who underwent arthrocentesis in our emergency department during a one-year period. Leukocyte esterase and glucose strip tests were performed on the synovial fluid. Synovial fluid leukocyte count, crystal analysis, Gram staining, culture, and glucose concentration results were also assessed.
RESULTS: Nineteen fluids were classified as septic and 127 as aseptic. Considering septic arthritis to be present when the leukocyte esterase reading was positive (++ or +++) and the glucose reading was negative (-) yielded a sensitivity of 89.5% (95% confidence interval [CI], 66.9% to 98.7%), specificity of 99.2% (95% CI, 95.7% to 99.9%), positive predictive value of 94.4% (95% CI, 72.7% to 99.9%), negative predictive value of 98.4% (95% CI, 94.5% to 99.8%), positive likelihood ratio of 114, and negative likelihood ratio of 0.11. The synovial leukocyte counts and polymorphonuclear cell percentages were consistent with the semiquantitative readings on the leukocyte esterase strip tests, and the glucose concentrations were consistent with the glucose strip test results.
CONCLUSIONS: Combined leukocyte esterase and glucose strip tests can be a useful additional tool to help confirm or rule out a diagnosis of septic arthritis. LEVEL OF EVIDENCE: Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.