Effectiveness of leucocyte esterase as a diagnostic test for acute septic arthritis.

Background: We hypothesized that leucocyte esterase strip test can aid in diagnosing septic arthritis in native synovial fluid because leucocyte esterase concentrations would be elevated at the infection site because of secretion by recruited neutrophils.

Method: The cohort included 27 patients (suspected septic arthritis and normal subjects). A standard chemical test strip (graded as negative, trace, +, ++ or +++) was used to detect the presence of leucocyte esterase. Fluid leucocyte count, Gram staining, culture, erythrocyte sedimentation rate and C-reactive protein were also assessed.

Results: The leucocyte esterase test with a threshold of ++/+++ had a sensitivity of 79.2% (95% CI [confidence interval], 65.9% to 89.2%), specificity of 80.8% (95% CI, 73.3% to 87.1%), positive predictive value (PPV) of 61.8% (95% CI, 49.2% to 73.3%) and negative predictive value (NPV) of 90.1% (95% CI, 84.3% to 95.4%).

Conclusion: The leucocyte esterase strip test yielded a high specificity, PPV, NPV, high sensitivity and high diagnostic accuracy. Leucocyte esterase is an accurate, quick and bedside test for septic arthritis and can be used effectively for diagnosing periprosthetic joint infections along with other battery of tests according to the Musculoskeletal Infection Society criteria.