Nitrites react with p-arsanilic acid to form a diazonium compound that reacts with a color reagent to produce a pink color on the strip. Normally no nitrite is present in urine. Test depends on conversion of dietary nitrate to nitrite by Gram negative bacteria in the urine. False positive tests-none. Absence of dietary nitrate.
Sensitivity is reduced for urine with high specific gravity.
Patient samples with less than 4 hours of bladder incubation. Optimum sample is obtained at first morning voiding.