Serum C-Reactive Protein to Hemoglobin Ratio: Novel Biomarkers for the Diagnosis of Chronic Periprosthetic Joint Infection

Abstract

Background: Despite several markers being evaluated and available in recent years, diagnosing periprosthetic joint infection (PJI) remains challenging. There is a pressing need to explore reliable, economical, convenient, highly sensitive, and specific diagnostic biomarkers to diagnose PJI. This study aimed to investigate the diagnostic value of combined serum markers with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) in PJI.

Methods: A total of 841 revision arthroplasty cases, including 435 PJI and 406 non-PJI patients, were enrolled from January 2010 through December 2022. The diagnostic values of CRP, ESR, CRP + ESR, CRP or hemoglobin ratio (CHR), CRP or albumin ratio, CRP or hemoglobin + albumin ratio, ESR or hemoglobin ratio, ESR or albumin ratio, ESR or hemoglobin + albumin ratio, and hemoglobin + albumin were evaluated using sensitivity, specificity, and receiver operating characteristics analysis with area under the curve. The optimal threshold was determined using the Youden index.

Results: The CHR had the highest area under the curve (0.87, 95% CI [confidence interval] 0.85 to 0.90) and sensitivity (0.81, 95% CI: 0.77 to 0.85), compared to other markers. The CHR exhibited reliable diagnostic adequacy for PJIs caused by low-virulent organisms (sensitivity 0.83, 95% CI: 0.76 to 0.89; specificity 0.83, 95% CI: 0.79 to 0.86). However, CHR displayed poor sensitivity (0.77, 95% CI: 0.67 to 0.86) in patients who have diabetes.

Conclusions: The CHR demonstrated better diagnostic strength in detecting chronic PJI than other classical markers, especially in identifying low-grade infections. Our findings offer new insights into a more accurate and comprehensive picture of pathogens and hosts, thereby improving the accuracy of diagnostic algorithms.

Keywords: biomarkers; chronic periprosthetic joint infection; diagnosis; hemoglobin; serum CRP.