The area under the ROC curve (AUC) for HBP in diagnosing PJI was 0.968 (95% CI: 0.943–0.993), outperforming CRP (0.760, 95% CI: 0.680–0.840), ESR (0.825, 95% CI: 0.753–0.896), IL-6 (0.875, 95% CI: 0.816–0.935), and PCT (0.663, 95% CI: 0.567–0.759). The gene discussed is ESR1; the disease is juvenile polyposis syndrome.