Poor predictive value of broad-range PCR for the detection of arthroplasty infection in 92 cases

Background The diagnosis of prosthetic infection remains a challenge, as no test is 100% sensitive and 100% specific. Recent advances in molecular biology have enabled the detection of infection in culture negative cases. Patients and methods We evaluated the effectiveness of polymerase chain reaction (PCR) in detecting infection in failed joint replacements prospectively in 91 consecutive patients (92 prosthetic joints) undergoing revision total hip or knee arthroplasty. Synovial fluid was collected intraoperatively and examined by broad-range PCR assay for detection of bacterial DNA. The clinical diagnosis of infection was based on the results of blood tests, preoperative joint aspiration, culture and histology of multiple intraoperative tissue samples, as well as the surgeon's assessment. 12 joints (13%) were infected, but the PCR was positive in 32 cases. The sensitivity of the technique was 92%, the specificity 74%, the accuracy 76%, the positive predictive value 34%, and the negative predictive value was 98%. Interpretation The PCR technique cannot be recommended for the routine detection of prosthetic infection. The large number of false positive results may represent sample contamination, or bacterial presence related to low-virulence organisms, low bacterial load, or a strong host immune response.