We further found that when synovial fluid IL-1β and synovial fluid PMN% were both above their thresholds of 312.7 pg/mL and 69.96%, respectively, and they could be used to identify a positive result for chronic PJI, with sensitivity, specificity, PPV, NPV, and accuracy of 91.89%, 100%, 100%, 94.92%, and 96.77%, respectively. The gene discussed is IL1B; the disease is juvenile polyposis syndrome.