How the urine is collected decides whether the culture can be trusted

In a child who is not toilet-trained, a bag specimen is useful only to rule out UTI: a negative dipstick on bag urine makes infection unlikely, but a positive result or growth is frequently contamination. If a bag sample is positive and treatment is being considered, confirm with a catheter or suprapubic sample before starting antibiotics where the child is well enough to wait.

In older children, a clean-catch midstream sample is appropriate. Label the collection method on the request, because interpretation depends on it.

• Do not rely on a bag urine culture to diagnose UTI in a child in nappies.
• Use catheter or suprapubic aspiration samples to confirm infection in young children.
• Use a clean-catch midstream sample in toilet-trained children.
• Write the collection method on every urine request.

Why it matters

Contaminated samples lead to unnecessary antibiotics, imaging and a false label of UTI.

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