Associations of C-reactive protein-albumin-lymphocyte (CALLY) index with cardiorenal syndrome: Insights from a population-based study

<h2>Abstract</h2><h3>Background</h3> Cardiorenal syndrome (CRS) is a complex condition characterized by the interplay of immune imbalance and inflammation. The C-reactive protein-Albumin-lymphocyte (CALLY) CALLY index serves as a new immune-nutritional scoring system, but its predictive value for CRS remains to be established. <h3>Methods</h3> In this study, we analyzed data from 27,978 participants in National Health and Nutrition Examination Survey (NHANES) from 1999 to 2010. The CALLY index was calculated as the ratio of albumin to lymphocyte, divided by C-reactive protein (CRP) multiplied by 10⁴. CRS was defined by the coexistence of cardiovascular disease and chronic kidney disease (eGFR <60 mL/min/1.73 m²). Multivariate weighted logistic regression models were employed to determine the odds ratio and 95 % confidence interval for the association between the CALLY index and CRS. Receiver operating characteristic (ROC) curves and restricted cubic spline (RCS) curves were used to assess the predictive efficacy and nonlinear relationship, respectively. <h3>Results</h3> The prevalence of CRS in the study population was 1.22 %. Our findings revealed a significant inverse relationship between the CALLY index and CRS risk, with lower CALLY index values being associated with a higher likelihood of CRS (OR = 0.95, 95 % CI = 0.94–0.96, P < 0.001). Participants in higher quartiles of the CALLY index showed a progressively reduced risk of CRS (P for trend <0.001). Moreover, the CALLY index demonstrated superior predictive performance compared to other inflammatory indicators, such as systemic immune-inflammation index (SII), neutrophil/high-density lipoprotein ratio (NHR), lymphocyte/high-density lipoprotein ratio (LHR), monocyte/high-density lipoprotein ratio (MHR), and platelet/high-density lipoprotein ratio (PHR) (AUC = 0.672, 95 % CI = 0.643–0.701). <h3>Conclusions</h3> This study underscores the significant negative correlation between the CALLY index and the risk of cardiorenal syndrome. The CALLY index emerges as a robust and independent predictor of CRS, outperforming traditional inflammatory markers. This finding highlights the potential utility of the CALLY index as a clinical tool for identifying individuals at risk for CRS.