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

## TL;DR

This study evaluates blood markers and ratios to help diagnose joint infections after hip replacement surgery.

## Contribution

The study introduces and evaluates new diagnostic ratios (AGR, CAR, CAGR) for periprosthetic joint infection detection.

## Key findings

- ESR, AGR, CAR, and CAGR showed acceptable diagnostic accuracy for periprosthetic joint infection.
- CRP and ESR had moderate accuracy, while WBC and TP had lower diagnostic value.

## Abstract

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.