Common Serum Biomarkers and Combination Ratios in the Diagnosis of Periprosthetic Joint Infection Following Total Hip Arthroplasty

Accurate preoperative diagnosis of periprosthetic joint infection (PJI) is difficult, complicating distinction between septic and aseptic failures. This study assessed the value of common serum biomarkers and three calculated ratios-albumin-globulin ratio (AGR), C-reactive protein-albumin ratio (CAR), and C-reactive protein-AGR ratio (CAGR)-in diagnosing PJI after primary total hip arthroplasty (THA). We retrospectively reviewed patients undergoing revision THA for PJI or aseptic failure from 2011 to 2021 at a single institution. Inclusion required reported serum white blood cell count (WBC), C-reactive protein (CRP), erythrocyte sedimentation rate (ESR), albumin (Alb), and total protein (TP). Diagnostic performance was evaluated using areas under the curve (AUCs), with higher values indicating better accuracy. Ratios were defined as: AGR = Alb/[TP - Alb], CAR = CRP/Alb, and CAGR = CRP/AGR. Among 128 cases, 67 were PJI and 61 aseptic. AUCs were: WBC (0.53), CRP (0.69), ESR (0.75), Alb (0.69), Glb (0.63), TP (0.53), AGR (0.72), CAR (0.70), and CAGR (0.71). Optimal cutoff, sensitivity, and specificity were: CRP (10.5, 0.76, 0.59), ESR (41.0, 0.70, 0.72), AGR (1.10, 0.64, 0.75), CAR (3.37, 0.73, 0.64), and CAGR (10.9, 0.75, 0.66). ESR, AGR, CAR, and CAGR demonstrated acceptable accuracy. These readily available markers and ratios may aid PJI diagnosis, supporting improved clinical decision-making.