2] The prevalence of this false-negative reaction does vary depending on reagent strip brand, with some brands showing greater sensitivity than others.
56), "Oxidizing agents such as hypochlorite and ascorbic acid cause false-negative reactions for blood on the urine dipstick," cannot be answered true or false.
Failure to add the anti-D reagent, heavy cell suspension, presence of contaminants in the sample, or under-centrifugation/incorrect calibration during testing can result in false-negative reactions
These have the benefit of controlling for false-negative reactions
at each well position.
3] False-negative reactions for both blood and sugar are a major problem if there is ascorbic acid in the urine.
Since few published studies of individual dipstick performance have included checks for urinary ascorbate, unsuspected urinary contamination with vitamin C may have been responsible for some of the false-negative reactions for hemoglobin and glucose noticed in earlier dipstick evaluations.