Razi Journal of Medical Sciences

  Background: Triggering receptors expressed on myeloid cells i.e soluble triggering expressed on myeloid cells-1 (STREM-1) is inducible on monocyte/macrophages and neutrophils and accelerates tissue destruction by propagating inflammatory responses in disease related to bacterial infections.

  The aim of this study was to investigate the role of STREM-1 in the synovial fluid to identify septic arthritis from aseptic ones.

  Methods: A cross sectional study (2007-2009) was conducted in the Pediatric & Orthopedic wards of Hazrat-e-Rasool Akram hospital, Tehran . Synovial fluid was aspirated in 53 cases with arthitis and searched for diagnosis of bacterial arthritis by conventional diagnostic tests. About 0.5-3cc of synovial fluid was stored at -70 °C, and quantification of STREM-1 was done in 53 synovial fluid samples (Quantikine, R&D systems, USA ) by EIA results were compared between septic and aseptic arthritis.

  Results: Septic arthritis was detected in 49% (26/53) and aseptic arthritis in 51%( 27/53). Positive synovial fluid culture was detected in 20.3%, and positive latex particle agglutination for bacteria was found in 8.5%. Positve direct smear was obtained in 10.5% of the cases.Cut off level 825 pg/ml for SF-STREM-1 yielded 50% sensitivity, 70% specificity, 64% Positive Predictive Value (PPV), and 64%, Negative Predictive Value (NPV). Poor agreement was seen between SF -STREM-1 levels and positive culture (p value: 0.037 Kappa=0.28) . The area under the ROC curve for discriminating between septic and aseptic arthitis was 0.603 (95% CI 0.757–0.448, p = 0.1).

  Conclusion: SF-STREM-1 level with cutoff 825pg/ml had 50% sensitivity, and 70 % specifity in discriminating between proved cases with septic arthitis from aseptic ones. Searching for bacterial antigens in synovial fluid (Latex Particle Aagglutination test) and synovial fluid -STREM-1 level could potentially assist clinicians in better diagnosis of septic arthitis if added to the conventional tests including smear and routine analysis of synovial fluid. It might prevent unnecessary empiric antibiotic theray in children with arthritis. In clinical decision making randomized studies on the potential synovial fluid - STREM-1 -level guided antimicrobial therapy in bacterial arthritis would be useful.