A dipstick reading blood is not microhaematuria. It detects peroxidase activity, which myoglobin, free haemoglobin, some oxidising contaminants and menstrual contamination all produce, and it does not count cells. Guidelines define microhaematuria by red cells per high-power field on microscopy, and the cell count itself carries risk information - 25 or more per high-power field marks a higher-risk group.
So the first step after a positive dipstick is a microscopic urinalysis, and the second is to look for the explanations that make further investigation unnecessary: a urinary tract infection to treat and recheck, recent vigorous exercise, menstruation, recent instrumentation or catheterisation, or a stone already known about. Recheck after treating or after the exposure has passed, before the patient enters an imaging and cystoscopy pathway.
What this prevents is a common and expensive sequence: a dipstick trace in an asymptomatic patient, a CT urogram, a cystoscopy, and a negative result that nobody needed. It also prevents the opposite error - the trace that gets dismissed as 'probably the dipstick' in a 65-year-old smoker, where it should have been counted and investigated.
- Confirm every positive dipstick with microscopy before starting an investigation pathway
- Record red cells per high-power field - the count itself stratifies risk
- Treat and recheck where there is infection; repeat after exercise, menstruation or instrumentation
- Do not dismiss a confirmed trace in an older smoker as a dipstick artefact
- Document the confirmatory result, so the next clinician does not restart the pathway
Why it matters
The dipstick and microscopy are not the same test, and the whole investigation pathway is defined by the one that is usually skipped.
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