Urine collection methods for infants under 3 months of age in clinical practice

Abstract

Methods of urine collection used in precontinent children are a controversial issue. Definitive diagnosis of urinary tract infection (UTI) requires an uncontaminated urine culture. We aimed to describe methods used to collect urine for culture in infants under 3 months of age and compare results and contamination rates. This retrospective observational cohort study included 721 urine cultures collected from infants <3 months of age at the Hospital Universitario Infanta Sofía, Madrid, between January 2016 and December 2019. Urine cultures were compared based on collection technique, sex, and patient age. Median patient age was 36 days and 54.6% were male. In total, 592 (82.1%) samples were collected using clean-catch urine stimulation technique (CCUST), 77 (10.7%) by urethral catheterization (UC) and 52 (7.2%) by urine bag (UB). Positive cultures were obtained in 11.7% (95% confidence interval [CI] 9.1, 14.3) of CCUST samples and in 28.6% (95% CI 18.5, 38.7) of UC samples (p<0.001). The contamination rate was 13.7% (95% CI 10.9, 16.4] for CCUST, 23.1% (95% CI 11.6, 34.6) for UB and 5.2% (95% CI 0.2, 10.2) for UC, with statistically significant differences (p=0.007) between UB and UC collection. CCUST is the most commonly used method in our hospital for collecting urine in infants younger than 3 months. The contamination rate of UC is lower but not significantly different to that of CCUST. Urine collection by CCUST serves as a non-invasive alternative to UC for diagnosis of UTI in infants under 3 months of age in routine clinical practice. Graphical abstract.