A bag specimen has a high false-positive rate and cannot confirm a urinary infection. In a febrile infant who needs antibiotics, obtain urine by catheter or suprapubic aspiration, or a clean-catch sample where the child is old enough, before the first dose, provided this does not delay antibiotics in a seriously ill infant.
A negative bag urine can help exclude infection, but a positive one needs confirming with a properly collected sample.
- Collect urine by catheter or suprapubic aspiration in febrile infants before starting antibiotics, unless this would delay treatment in a seriously ill infant.
- Do not diagnose a urinary infection from a positive bag specimen alone.
- Send the sample for culture as well as dipstick or microscopy.
- Review the culture result at 48 hours and adjust or stop antibiotics.
Why it matters
A false diagnosis from a bag sample leads to unnecessary imaging, antibiotics and follow-up.
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