Association of C-Reactive Protein–to-Albumin Ratio and Clinical Factors With Hospitalization Duration in Urinary Tract Infections: A Retrospective Cohort Study

Objective: To evaluate whether the admission C-reactive protein–to-albumin ratio (CAR), combined with clinical characteristics, is associated with prolonged hospital stay in adults hospitalized with urinary tract infection (UTI). Methods: This retrospective cohort study evaluated adults hospitalized with UTI at 2 centers (August 2023–November 2024). Prolonged stay was defined as 7≥ days (cohort median). CAR, calculated from C-reactive protein and albumin within 24 hours of admission, was analyzed as a continuous variable using receiver operating characteristic (ROC) analysis, univariable and multivariable logistic regression, and linear regression of log-transformed length of stay. Results: Among 59 patients, 38 (64.4%) were female, 31 (52.5%) had upper UTI, and 38 (64.4%) had a hospital stay of 7≥ days. The area under the ROC curve [AUC] for CAR was 0.64 (95% CI, 0.50–0.78; P = .07). Higher CAR was associated with prolonged stay in univariable analysis (OR, 1.37 per 10-unit increase; 95% CI, 1.01–1.85). After adjustment for age and infection site, this estimate was similar but less precise (adjusted OR, 1.43; 95% CI, 0.97–2.11); however, age (adjusted OR, 1.13 per year; 95% CI, 1.02–1.25) and upper UTI (adjusted OR, 6.61; 95% CI, 1.64–26.64) were independently associated with prolonged stay. Analyzing length of stay as a continuous outcome, each 10-unit increase in CAR was associated with a 4.8% higher adjusted geometric mean stay (95% CI, 1.9%–7.8%). Conclusions: Older age and upper urinary tract involvement were independently associated with prolonged stay. Higher CAR was associated with longer stay, but after multivariable adjustment, the estimate was imprecise and compatible with no association, with limited discriminative ability. These exploratory findings require validation in larger prospective cohorts.