Evaluation of reagent strips for the rapid diagnosis of nitrite poisoning

Two commercial urine test strips based on the Griess nitrite-specific diazonium salt reaction, having sulfanilamide and para-arsanilic acid as substrates, respectively, were studied as qualitative tests in the rapid diagnosis of nitrite/nitrate poisoning. Their usefulness was compared to other rapid tests, such as the sulfanilic acid-1 naphthylamin and diphenylamine blue tests. The practical sensitivity limit to nitrites in plasma and in water of both the reagent strips and SA-1NA test was 0.50 micrograms NO2/mL, while the diphenylamine test, which is not nitrite specific, showed a positive reaction to nitrites in plasma and in water above 50 micrograms NO2/mL and 5 micrograms NO2/mL, respectively. The in vitro assays were evaluated in vivo by the sublethal intoxication of a sheep with nitrite, demonstrating that commercial urine test strips may be useful for the rapid diagnosis of nitrite/nitrate poisoning.