Adjunctive Value of Admission CBC-Derived Inflammation Indices for Catheter-Related Bloodstream Infection in Catheter-Dependent Hemodialysis Patients: A Retrospective Case–Control Study

Background/objectives: Catheter-related bloodstream infection (CRBSI) is a frequent and morbid complication in catheter-dependent maintenance hemodialysis, and rapid risk stratification is needed while awaiting cultures. This study aimed to evaluate admission complete blood count-derived indices—neutrophil-to-lymphocyte ratio (NLR), lymphocyte-to-monocyte ratio (LMR), platelet-to-lymphocyte ratio (PLR), systemic immune-inflammation index (SII), and pan-immune-inflammation value (PIV)—for identifying CRBSI. Methods: This single-center retrospective study (1 January 2011–31 October 2024) included adult catheter-dependent hemodialysis patients classified as CRBSI or controls. CRBSI required compatible clinical findings and concordant growth of the same microorganism(s) in paired simultaneous catheter and peripheral blood cultures. Controls were hospitalized for non-infectious reasons without infection during the index admission. Indices were calculated from admission blood counts. Discrimination was assessed using ROC analysis, and adjusted associations were evaluated using multivariable logistic regression. Results: Among 286 patients (147 CRBSI, 139 controls), CRBSI cases had higher NLR, SII, and PIV and lower LMR; PLR did not differ. NLR showed the numerically highest discriminatory performance among the evaluated indices (AUC 0.737; cut-off 5.96; sensitivity 68.7%, specificity 68.3%; p < 0.001). SII (cut-off 1189.21; AUC 0.693) and PIV (cut-off 821.62; AUC 0.686) had moderate discrimination, and LMR was modest (cut-off 1.65; AUC 0.642); PLR was not discriminatory (AUC 0.559; p = 0.086). In models adjusted for age, sex, hypertension, and cardiovascular disease, NLR remained associated with CRBSI (OR 1.159; p < 0.001), together with hypertension (OR 2.441; p = 0.017) and cardiovascular disease (OR 2.626; p < 0.001). Conclusions: Admission hematologic inflammation indices, particularly NLR, showed moderate ability to discriminate CRBSI from non-infectious admissions in catheter-dependent hemodialysis patients and may provide rapid adjunctive information while awaiting microbiological confirmation.