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A urine drug screen cannot differentiate between the drug being tested for and any drugs that may cross-react with the test. The pseudoephedrine can cause a false positive, but the test will only return as positive. It is recommended that when there is a positive screen, that the urine be sent for a confirmatory test, such as gas chromatography/mass spectrometry (GC/MS). The confirmatory test is able to differentiate between the methamphetamine and the pseudoephedrine. Therefore, if someone provides urine for testing, although the screen would not be able to differentiate, the confirmatory test would be able to do so.
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