They suggest that testing the serum of patients alone is not enough and the false positive results could be avoided by adding urine tests as well.

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For example, a probation program in Hawaii in 2004 substantially increased the chances that "dirty" urine tests for illegal drugs would result in jail time (brief stays of a few days).

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Students must also take weekly random urine tests.

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Players already undergo random urine tests.

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She started in 1946 as a receptionist in the lab, where she helped out by catheterizing male frogs to get the urine specimens used in pregnancy tests at the time.

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While doctors can perform a variety of tests on an unconscious person without his or her consent if they feel they could help determine the source of the problem, a conscious patient in casualty would have to give permission for urine samples to be taken, and the tests could not be made a pre-condition of treatment.

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If Landis' backup urine sample is positive - and the backup or B-tests often confirm the original - Landis could be stripped of his title.

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