Diagnostic Performance of Hematological Blood Ratios in Revision Surgery for Periprosthetic Joint Infections: A Retrospective Cohort Analysis of CRP/Hb Ratio, NLR, and MLR

Objectives: Periprosthetic joint infections represent a serious complication following joint arthroplasty, often leading to significant morbidity, with an economic and social impact on the health system. Timely diagnosis of periprosthetic joint infections remains a major challenge. Our study aimed to investigate the diagnostic value and accuracy of several markers, including the neutrophil-to-lymphocyte ratio, monocyte-to-lymphocyte ratio, and C-reactive protein-to-serum-hemoglobin ratio in revision surgery for periprosthetic joint infections. Methods: A total of 251 revision arthroplasty cases, including 137 cases of periprosthetic joint infections and 114 cases of aseptic revision arthroplasty, were included from the time span January 2016 to May 2025. The diagnostic value and accuracy of the C-reactive protein-to-hemoglobin ratio, neutrophil-to-lymphocyte ratio, and monocyte-to-lymphocyte ratio were evaluated using sensitivity, specificity, and receiver operating characteristic (ROC) analysis with area under the curve analysis. Results: The highest diagnostic performance was obtained by the C-reactive protein-to-hemoglobin ratio, yielding an AUC of 0.859 (SE = 0.0263, 95% CI: 0.809–0.899). This ratio also demonstrated a strong discriminative capacity, with a threshold of >0.0667, sensitivity of 80.45%, and specificity of 85.96%. For the neutrophil-to-lymphocyte count ratio and monocyte-to-lymphocyte count ratio, we obtained an AUC of 0.615 (95% CI: 0.551–0.676) and 0.620 (95% CI: 0.556–0.680), respectively, demonstrating lower sensitivity and specificity than the C-reactive protein-to-hemoglobin ratio. Conclusions: The C-reactive protein-to-hemoglobin ratio demonstrated better diagnostic strength in detecting periprosthetic joint infections, with superior sensitivity and specificity compared to the neutrophil-to-lymphocyte count ratio and monocyte-to-lymphocyte count ratio. Our findings offer new insights into the accurate and early diagnosis of periprosthetic joint infections in cases requiring revision surgery and suggest incorporating these new biomarkers and ratios into the diagnostic algorithm. Future large-scale studies are further needed to validate these results and facilitate their clinical use.