Do nitrates in urine always prove uti?

Almost: The chance that a person has a UTI if their nitrite test is positive is 92 to 100 percent, depending on which study you look at.

No they don't: About 90%+ accurate. Nitrites are negative with enterococcus, UTIs also the less common staphlococcal & streptococcal infections. Have also seen occasional E. coli & proteus UTIs test negative. Hence need for a urine culture especially.if subect is symptomatic & has white blood/pus cells in urine.