The neutrophil-to-lymphocyte ratio is associated with bacteremia in older adults visiting the emergency department with urinary tract infections.

Purpose: We evaluated the clinical features of older adults visiting the emergency department (ED) with urinary tract infections (UTIs), and the diagnostic utility of the neutrophil-to-lymphocyte ratio (NLR) in terms of identifying bacteremia.

Methods: In total, 479 older adults admitted with UTIs via the ED between January 2010 and December 2015 were retrospectively reviewed. We recorded age, sex, comorbidities, body temperature, clinical findings, and initial laboratory results, including the NLR.

Results: A UTI with bacteremia was identified in 186 (38.8%) older adults. Bacteremia was associated with a longer hospital stay (median 10 vs. 8 days, p < 0.001). NLRs and C-reactive protein, blood urea nitrogen and creatinine levels were significantly higher in the bacteremia group than in the non-bacteremia group (p < 0.001, p = 0.016, p = 0.008, and p = 0.011, respectively). The area under the curve for the NLR was 0.624 (95% CI = 0.579-0.668, p < 0.001), and the cutoff was 9.0 (sensitivity 74.2, specificity 49.2%). Independent risk factors for bacteremia were an NLR ≥ 9 and fever ≥ 39 °C (OR 2.43, OR 2.75: p < 0.001, p < 0.001, respectively).

Conclusion: Bacteremia was associated with a longer hospital stay in older adults with UTIs, in whom the initial NLR and high fever reliably predicted bacteremia. The NLR may help emergency physicians to predict bacteremia in older adults with UTIs visiting the ED.