ROC analyses (Fig. 3 and Table 4) indicated that CRP/AGR performed best in diagnosing PJI (AUC: 0.902, 95% CI: 0.845–0.943; optimal cutoff: 5.08), followed by CRP (AUC: 0.896, 95% CI: 0.838–0.938; optimal cutoff: 6.59 mg/L) and ESR (AUC: 0.829, 95% CI: 0.763–0.883; optimal cutoff: 34 mm/h). Here, CRP is linked to juvenile polyposis syndrome.