Impact of cleaning before obtaining midstream urine samples from children

Microbiological documentation of one uropathogenic bacterium in significant numbers in urine from patients with typical symptoms is the gold standard for diagnosing urinary tract infection (UTI). Cleaning before collecting midstream urine (MSU) is reported not to reduce the risk of contaminating the sample and was therefore omitted at Hvidovre Hospital as from the autumn of 2006. We evaluate if no cleaning increased the risk of contamination in the Department of Paediatrics.

A total of 1,858 patients aged 0-15 years who were suspected of UTI delivered two MSUs within 24 h. In 2004-2006 ("cleaning period"), 523 children were cleaned before obtaining two MSUs, contrary to the 1,335 children included in 2008-2010 ("non-cleaning period"). Significant bacteriuria was defined as at least 10,000 colony-forming units/ml of the same uropathogenic bacterium in two MSUs in monoculture. Contamination was defined as all other microbiological findings.

The procedure of no cleaning before sampling increased the risk of contamination in 0-9.9-year-old children from 43% to 49% (p = 0.034); and specifically in 0-9.9-year-old girls, the risk of contamination increased from 47% to 55% (p = 0.018). No significant effect was demonstrated in 10-15-year-old girls (p = 1.0) or in boys, independent of age (p = 0.19). In both periods, 31% of paired MSUs from the same child were without any bacterial or fungal growth.

Cleaning before collecting urine from girls younger than ten years of age is recommended to minimise the risk of contamination. Cleaning was without effect on children aged 10-15 years.

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