Positive urine culture and negative Urinalysis in 4 year old?

[A2010]

My 4 year old daughter has been experiencing lethargy and tummy pains for the last 7 days. She’s had 2 urine samples taken, one at the doctors which was completely clear, and one at the hospital which was sent to the lab and has come back positive for ecoli. I’m just puzzled how one can be negative and one is positive. Anyone have any ideas?

Sometimes one sample has been contaminated (usually by stool, which is full of e coli). Sometimes it's just one of those things, no test is 100% reliable.

Was the one at the doctors just a dipstick test? They aren’t entirely reliable and can be negative even if there is an infection.