Procedural Considerations

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The page below is a sample from the LabCE course Chemical Screening of Urine by Reagent Strip (retired March 2012). Access the complete course and earn ASCLS P.A.C.E.-approved continuing education credits by subscribing online.

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Procedural Considerations

Although the procedure is simple to perform, accurate results depend on careful adherence to manufacturer's directions and adequate quality control.

  • Normal and abnormal controls should be tested whenever a new lot of strips is opened, and at the frequency defined by the laboratory's procedure.
  • If quality control results do not correspond to the published control values, the problem must be resolved before patient samples are tested.
  • High levels of ascorbic acid (Vitamin C) in the urine may inhibit some reagent strip reactions, such as glucose, blood, bilirubin, nitrate and leukocyte esterase. The urine dipstick's package insert will provide information about potential interfering substances, including ascorbic acid.
  • Intensely colored urine may make it difficult to correctly interpret color reactions on the dipstick, as demonstrated in the image on the right. The affected tests should not be reported from the dipstick. It would be necessary to use an alternative method of testing if available.