False-negative results may occur with any of the following: Infection with certain pathogens that cannot convert nitrate to nitrite (eg, Enterococcus faecalis, Neisseria gonorrhoeae, Mycobacterium tuberculosis) Urine that has not stayed long enough (< 4 hours) in the bladder Low urinary excretion of nitrate Enzymes (of certain bacteria) that reduce nitrates to nitrogen High urine urobilinogen level Presence of ascorbic acid Urine pH < 6.0 Nitrites are used mainly with WBC esterase testing to monitor patients with recurrent urine infections, particularly children with vesicoureteral reflux, and sometimes to confirm the diagnosis of uncomplicated urinary tract infection (UTI) in women of childbearing age.