Diagnosis of periprosthetic joint infection using synovial C-reactive protein.

The diagnosis of periprosthetic joint infection (PJI) is a considerable challenge. This study examines the quantification of C-reactive protein (CRP) in synovial fluid for diagnosis of PJI. Synovial fluid samples were collected prospectively from 63 patients undergoing revision or primary joint arthroplasty. All patients were divided into septic vs aseptic groups. There were 43 patients in the aseptic group and 20 patients in the septic group. There was a statistically significant difference in the mean synovial CRP between the septic cohort at 40 mg/L vs a mean of 2 mg/L for aseptic failure (P < .0001). The sensitivity was 85% with 95% specificity at a threshold of 9.5 mg/L. The area under the curve was 0.92. We believe that synovial CRP assay holds great promise as a diagnostic marker for PJI.