Contamination rates of different urine collection methods for the diagnosis of urinary tract infections in young children: an observational cohort study

Aims: The optimal method for diagnostic collection of urine in children is unclear. National Institute of Health and Clinical Excellence recommend specimens taken by clean catch urine (CCU) for identification of urinary tract infection (UTI). We investigated contamination rates for CCU, suprapubic aspiration (SPA), catheter specimen urine (CSU) and bag specimen urine (BSU) collections.

Method: Retrospective observational cohort study with review of microbiology data and medical records at a large tertiary children's hospital. We reviewed urine culture growth from consecutive first urine specimens of children aged <2 years, over a 3-month period in 2008. Patient demographics, collection method, location (emergency department, inpatient ward), culture growth, history of UTI, urogenital tract abnormality and antibiotic use were assessed. Contamination rates for collection methods were compared using logistic regression.

Results: Urine culture specimens of 599 children (mean age 7.0 months, 54% male) were included. There were 34% CCU, 16% CSU, 14% SPA, 2% BSU and 34% with unknown sample method. Contamination rates were 26% in CCU, 12% in CSU (odds ratio (OR) 0.4, 95% confidence interval (CI) 0.2-0.8) and 1% in SPA (OR 0.03 95% CI 0.0-0.3). Concurrent antibiotics use was associated with a lower contamination rate. Contamination rates were not associated with age, sex, location, history of UTI or urogenital abnormalities.

Conclusion: Contamination rates in CCU are much higher than in CSU and SPA samples. Ideally, SPA should be used for microbiological assessment of urine in young children. Collection procedures need to be optimised if CCU is used.