In this study we evaluated the performance of the newly available ITI-Cartridge (UniveroTM i60 implant and tissue infection (ITI) multiplex polymerase chain reaction (PCR) System, Curetis®, Holzgerlingen, Germany) in diagnosing periprosthetic joint infection (PJI). 30 patients that received an operative revision in the orthopaedic department of the University Hospital Bonn due to suspected PJI or aseptic loosening of a painful total hip or knee arthroplasty between Januar 2014 and November 2014 were included in this retrospective study. The microbiological workup included a minimum of three periprosthetic tissue specimens, joint aspirate and the explanted foreign body for sonication were investigated. Additionally, histopathological examination of the periprosthetic membranes, cell counting of the joint aspirate and multiplex PCR diagnostic of the sonication fluid cultures and of the joint aspirate were performed. All patients were summarized in two diffrent groups (PJI vs. free of infection) according to the classification of the International Consensus Group on Periprosthetic Joint Infection [4]. In our collective sonication fluid cultures had a sensitivity of 88.89% with a specificity of 61.54%. Other microbiological specimens, especially tissue samples and joint aspirates showed both a sensitivity of 66.67%, and a specificity of 92.31% and respectively 84.62%. PCR-based rapid testing of sonication fluid yielded out a sensitivity of 50% with a specificity of 100%. PCR of the joint aspirate documented a slightly better sensitivity of 55.56 % with a specificity of 100%. When summarized these two PCRs the sensitivity rose to 66.67% with a specificity of 100%. In summary, PCR-diagnostic is an additional method to gain ancillary informations in diagnosing PJI but it has to be interpretated carefully in synopsis with the results obtained from tissue cultures, sonication fluid cultures, histopathological examination and clinical course. The performance of the newly available multiplex PCR system ITI-Cartridge did not persuade us, so that PCR diagnostic of sonication fluid culture or joint aspirate was not included in our algorythm of diagnosing PJI.
