Sensitivity, specificity, and receiver operating characteristic curve analysis were performed to assess for diagnostic performance.<h4>Results</h4>Five biomarkers, including human α-defensin 1-3, neutrophil elastase 2, bactericidal/permeability-increasing protein, neutrophil gelatinase-associated lipocalin, and lactoferrin, correctly predicted the MSIS classification of all patients in this study, with 100% sensitivity and specificity for the diagnosis of PJI. The gene discussed is BPI; the disease is juvenile polyposis syndrome.