Serum Calprotectin Demonstrates Moderate Diagnostic Performance for Detecting Periprosthetic Joint Infection in Hip and Knee Arthroplasty

Background Periprosthetic joint infection (PJI) is a serious complication after total hip and knee arthroplasty, with limited accuracy of conventional biomarkers. This study assessed serum calprotectin (CP) alongside established markers in revision arthroplasty. Methods This retrospective single-center study included 399 patients (232 total knee arthroplasty, 167 total hip arthroplasty). Based on Musculoskeletal Infection Society 2018 criteria, 132 patients were diagnosed with PJI and 267 were classified as non-PJI. All patients underwent serum CP, C-reactive protein (CRP), and interleukin-6 (IL-6) testing; microbiological analyses were performed when indicated. Results Serum CP was significantly higher in PJI than aseptic revisions (median 11,700 ng/mL [interquartile range 8080-18,675] vs 5,440 ng/mL [interquartile range 3600-8300], P < .001). The optimal CP threshold for PJI was 8,330 ng/mL (area under the curve=0.790, 95% CI, 0.741-0.838), providing a sensitivity of 65.2% (95% CI, 56.7-72.7%) and a specificity of 79.8% (95% CI, 74.6-84.2%). CRP and (IL)-6 showed higher diagnostic performance, with sensitivities of 69.0% (95% CI, 60.6-76.2%) and 73.6% (95% CI, 65.4-80.5%) and specificities of 88.4% (95% CI, 83.9-91.6%) and 85.0% (95% CI, 80.2-88.8%). Serum CP levels were not significantly influenced by joint type, sex, or age. In 8 patients with PJI, serum CP was above the cohort-derived threshold while both CRP and IL-6 remained below their respective thresholds. Conversely, in 10 cases, serum CP remained below the threshold despite elevated CRP and IL-6. Conclusions Serum calprotectin demonstrated moderate diagnostic performance and may may complement conventional serum markers in selected cases in which conventional serum markers are inconclusive.