Quantitative evaluation of periprosthetic infection by real-time polymerase chain reaction: a comparison with conventional methods

Several recent studies have demonstrated the limited accuracy of conventional culture methods for diagnosing periprosthetic infections. We have applied real-time polymerase chain reaction (PCR) assays for the rapid identification of bacteria around implants and reported its utility. However, the capability of quantification is also a useful feature of this type of assay. The aim of our study was to validate the usefulness of quantitative analyses using real-time PCR of cases with clinical periprosthetic infections in comparison with more established tests, such as C-reactive protein (CRP) levels, microbiologic cultures, and histopathology. Fifty-six joints with suspected infections were reviewed retrospectively. A universal PCR assay was used to perform the quantitative analyses. The differences in the threshold cycles between clinical samples and a negative control (Delta Ct) in each case were calculated. The results of the quantitative PCR assay were compared with CRP levels, microbiologic cultures, and histopathology. There was a significant correlation found between the CRP and Delta Ct values. There were also significant differences found in the Delta Ct values according to CRP levels, with higher CRP levels showing higher Delta Ct values. Similarly, there were significant differences in the Delta Ct measurements in our culture results and among our pathologic evaluations. We confirmed that quantification by universal PCR based on the Delta Ct correlated with preoperative CRP levels and was associated with the microbiologic culture results and pathologic severity. This quantification method may be valuable for assessing infection severity. (C) 2012 Elsevier Inc. All rights reserved.