Purpose: Prosthetic joint infection (PJI) is a devastating complication of total joint arthroplasty. No single laboratory test has perfect sensitivity and specificity; however, culture of periprosthetic tissue is the standard method for PJI diagnosis. Interpretation of positive culture results in PJI diagnostics can be difficult due to the possibility of contamination with microorganisms originating from skin micro flora. Criteria have been established to aid in distinguishing pathogen from contaminant for culture results. A similar criterion has not however been established for polymerase chain reaction (PCR) analysis, which is in part responsible for confusion about the reliability of PCR for PJI diagnostics. The aim of our study was to establish a criterion for interpretation of broad range (BR) PCR results in PJI diagnostics.
Methods: Samples of periprosthetic tissue were retrieved from 100 patients with joint prosthesis failure and analysed with BR-PCR. The results of BR-PCR were evaluated based on the number of samples of periprosthetic tissue with the same bacterial species.
Results: The sensitivity (87.5%) of BR-PCR was highest if the same species was present in at least one sample, although this criterion also resulted in the lowest specificity (92.1%). The sensitivity decreased (83.2%), although without a statistically significant difference, if the same species was present in two or more samples but, at the same time, specificity increased (100%), with a statistically significant difference.
Conclusions: For diagnostics of PJI with BR-PCR the criterion of the same bacterial species in at least two specimens of periprosthetic tissue from the same patient should be used for interpretation of positive results.