Ruling out underlying infection in 200 presumed aseptic knee and hip revision arthroplasties using a multiplex PCR system

Ruling out an infection in one-stage knee and hip revisions for presumed aseptic failure by conventional tissue cultures takes up to 14 days. Multiplex polymerase chain reaction (mPCR) is a quick test (4–5 h) for detecting pathogens. The purpose of this study was to evaluate the diagnostic accuracy of an automated mPCR of synovial fluid obtained intraoperatively in unsuspected knee and hip revisions. A prospective study was conducted with 200 patients undergoing a one-stage knee or hip revision. Synovial fluid was analyzed with the mPCR Unyvero implant and tissue infection G2 cartridge (U-ITI G2) system and compared to intraoperative tissue cultures. The primary outcome measure was the diagnostic accuracy, including sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV), of the mPCR U-ITI G2 system compared to conventional cultures. In the knee revision group, there were no patients with a positive mPCR in combination with positive cultures. This resulted in a non-calculable sensitivity and PPV. The specificity and NPV in the knee revision group of the mPCR compared to tissue cultures was 96.8% and 96.8%, respectively. In the hip revision group, the sensitivity, specificity, PPV, and NPV of the mPCR compared to tissue cultures was 36.4%, 96.6%, 57.1%, and 92.5%, respectively. Sixteen mismatches occurred between the mPCR and tissue cultures. The mPCR U-ITI G2 system is a quick and reliable synovium fluid test for ruling out infection in presumed aseptic knee and hip revisions with a high NPV compared with tissue cultures, although some mismatches were observed. Periprosthetic tissue cultures are still advised as back-up for false negative and positive mPCR test results.