False-Positive and False-Negative Results

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The page below is a sample from the LabCE course Chemical Screening of Urine by Reagent Strip. Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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False-Positive and False-Negative Results

A false-positive or falsely elevated result may be caused by vaginal contamination of the urine specimen or a highly pigmented specimen.
False-negative results may occur in the presence of significantly elevated protein, glucose, ascorbic acid, or specific gravity (significantly elevated specific gravity can crenate the white blood cells, leaving them unable to release esterases). The drugs cephalexin and gentamicin may also cause a false-negative result.