So as a urologist, my brief guide would be this.
The dipstick does throw up a number of false positive results, and ,as a chemical reagent test, is inferior to the direct urine lab microscopy (" MSU MC & S).
On most labs, < 10 RBC would be normal. An example is pasted below :
Urine
pH 7
Protein Nil
Glucose Nil
Blood Nil
Ketones Nil
Bilirubin Nil
Specific gravity 1.016 (1.005 - 1.030)
Microscopy
Leucocytes 3 x10^6/L ( <10 )
RBC Erythrocytes 3 x10^6/L ( <10 )
Epithelial cells 0 x10^6/L
Casts NIL
Culture No growth
Thus I rely on that, and urine cytology and ultrasound, to then decide who needs cystoscopy.
(Take also in context of AUA , EAU and BAUS guidelines).
Cheers,
Graham.