A Novel Integrated Biomarker for Predicting Post-Percutaneous Nephrolithotomy Infectious Complications: Retrospective Evaluation of the CALLY Index

Objective: This study aimed to evaluate the predictive value of the C-reactive protein-albumin-lymphocyte (CALLY) index, along with other inflammatory and nutritional markers, for early postoperative fever and its progression to systemic inflammatory response syndrome (SIRS) after percutaneous nephrolithotomy (PCNL). Material and Methods: This retrospective cohort study included 293 patients who underwent PCNL with sterile preoperative urine cultures. Postoperative fever was defined as an axillary temperature of ≥38 ℃, and SIRS was defined as the presence of two or more criteria within 48 hours post-PCNL. Preoperative inflammatory and CALLY indices were calculated. Logistic regression and receiver operating characteristic curve analyses were used for predictive values. Results: Of the 293 patients, 65 (22.2%) developed postoperative fever. Among the febrile patients, 31 (47.7%) had SIRS. Multivariate analysis identified CALLY as the sole independent predictor of both postoperative fever in the whole cohort (odds ratio=0.434, p=0.002) and SIRS in febrile patients (odds ratio=0.079, p=0.031). Higher CALLY scores were associated with lower odds of developing complications in the study population. CALLY demonstrated good discriminatory ability for postoperative fever (area under the curve=0.823; cutoff ≤1.365, sensitivity of 81.54%, specificity of 67.11%) and SIRS (area under the curve=0.757; cutoff ≤0.705, sensitivity of 83.87%, specificity of 64.71%). Conclusion: The preoperative CALLY index is a novel and independent predictor of both early postoperative fever and SIRS following PCNL in patients with sterile preoperative urine. Its nature of integrating nutritional status, immune response, and inflammation, provides a valuable tool for risk stratification, guiding individualised monitoring and timely intervention strategies following PCNL.