Determination the Cut off Level for Synovial S-Tream1 to Differentiate Septic from Aseptic Arthritis: A Cross Sectional Study, Tehran, Iran

Abstract

Objective: To evaluate the usefulness of STREM-1 level in synovial fluid (SF) to differentiate septic from aseptic arthritis. Methods: A cross sectional study performed in the Pediatrics ward of Rasoul Hospital, Tehran, IRAN (2008- 2009). Out of 66 children, 53 synovial fluid (SF) samples studied. Direct gram stain, conventional and Bactec culture, quantification of STREM-1 level (EIA Quantikine, RD S. Aureus (7/18, 38%). SF-STREM-1 Cut off level 825 pg./ml yielded 50% sensitivity, 70% specificity, 64% PPV, 64% NPV. The AUC was 0.603 (95% CI; 0.448-0.757, P = 0.2). SF-STREM-1 Levels were higher in patients with bacterial arthritis in compare with aseptic arthritis (95% Confidence Interval Odds Ratio 9.852-1.039; fisher exact test; P value: 0.056). Conclusion: SF-STREM-1 level even in very low amount (825 pg/ml) had intermediate (50%) sensitivity for diagnosis of septic arthritis. 70% specificity is excellent and sufficient for definite diagnosis, but it could misdiagnosed just in 30% of septic arthritis cases ( from other inflammatory arthritis), 64% NPV or the test is a limited factor. In our opinion the presence of STREM-1 in SFA can potentially assist clinicians in the diagnosis of half but not all cases with bacterial arthritis. The Positive SF culture as gold-standard test for diagnosis would obtain up to 80%. Combination of new biologic markers (PCT and sTREM-1) in SFA could be more helpful in high suspicious cases with negative culture (already on antibiotic treatment; or normally under growth of SF culture).