Evaluation of synovial calprotectin by using a lateral flow stool test for the diagnosis of prosthetic joint infections

The analysis of synovial fluid is a crucial step in the diagnostic process of prosthetic joint infections (PJI) and several studies illustrated the efficacy of synovial calprotectin in supporting the diagnosis of PJI. In this study, synovial calprotectin was analyzed by a commercial stool test to explore whether the detected levels might predict PJIs. The synovial fluids of 55 were analyzed. Calprotectin levels were compared to other synovial biomarkers of PJI. Of the 55 synovial fluids, 13 patients were diagnosed with PJI and 42 with an aseptic failure of the implant. The specificity, sensitivity, and AUC of calprotectin resulted 0.90, 0.85, and 0.86 (95%CI: 0.72-0.99), respectively with a set threshold of 226.5 µg/g. The values of calprotectin had a moderate and statistically relevant correlation with the synovial leucocyte counts (rs = 0.54, p = 0.0003) and percentage of synovial neutrophils (rs = 0.68, p = 0.0000). From this analysis, it can be concluded that synovial calprotectin is a valuable biomarker that correlates with other established indicator of local infection, and the use of a commercial lateral flow stool test could be a cost-effective strategy delivering rapid and reliable results and supporting the diagnostic process of PJI.