Different diagnostic properties of C-reactive protein, real-time PCR, and histopathology of frozen and permanent sections in diagnosis of periprosthetic joint infection

Background and purpose There are several diagnostic tests for periprosthetic joint infection (PJI). We evaluated the properties of preoperative serum C-reactive protein (CRP), real-time polymerase chain reaction (PCR), and histopathological evaluation of frozen and permanent sections in clinical cases with culture-positive PJI. Patients and methods 63 joints involving 86 operations were analyzed using serum CRP measurement prior to operation and tissue samples were collected intraoperatively for real-time PCR and histopathology. We calculated the sensitivity, specificity, likelihood ratio of positive test results (PLR), and likelihood ratio of negative test results (NLR) for each test in relation to positive microbiological culture results as the gold standard. Results The sensitivity and specificity of diagnosis with serum CRP were 90% and 85%, respectively. The corresponding values for real-time PCR and histopathology of frozen and paraffin tissue sections were 90% and 45%, 71% and 89%, and 90% and 87%, respectively. Serum CRP had a PLR of 5.8 and an NLR of 0.12, and real-time PCR had a PLR of 1.6 and an NLR of 0.18. The corresponding figures for frozen tissue sections were 6.6 and 0.32, and those for paraffin sections were 7.1 and 0.11, respectively. Interpretation The results suggest that real-time PCR and histopathology of frozen sections is a good combination. The former is suitable for screening, with its high sensitivity and good NLR, while the latter is suitable for definitive diagnosis of infection, with its excellent specificity and good PLR.