High Accuracy of Second Generation Unyvero ITI Automated Multiplex PCR Analysis of Joint Fluid Aspirate in Low-Grade Prosthetic Hip and Knee Joint Infections

AIMS AND OBJECTIVES: A major obstacle for the treatment of prosthetic joint infections (PJIs) is the identification of the organism causing it. While the diagnostic criteria ruling PJIs in or out have become ever more accurate, detecting the causative pathogen(s) still relies mostly on conventional culture. The aim of this study was to evaluate the diagnostic potential of a second generation multiplex PCR assay (Unyvero ITI G2, Curetis AG, Holzgerlingen, Germany) used on synovial fluid specimens. MATERIALS AND METHODS: Prospectively collected frozen joint fluid specimens from 26 patients undergoing arthroplasty revision surgery of the hip or knee for any reason were tested as per the manufacturer’s protocol. The sensitivity and specificity were calculated using the Chi-squared-test and a combination of the serum CRP level, leukocyte count, erythrocyte sedimentation rate, joint fluid culture, tissue biopsy culture, and tissue biopsy histology served as gold standard. RESULTS: Of the 26 cases included in the study, 15 were infected and 11 aseptic. Conventional joint fluid culture showed a sensitivity 0.67 and a specificity of 0.91. Joint fluid multiplex PCR yielded a sensitivity of 0.8 and a specificity of 1.0. CONCLUSION: This is the first study to assess the second generation Unyvero ITI cartridge on joint fluid aspirate for the detection of prosthetic joint infection. In our setting, the method achieved a higher diagnostic accuracy than conventional culture. We conclude that, to improve pathogen detection before revision surgery, this method represents a valuable tool.