A
positive screen is indicative that the subject screened positive
for the drug class in question. No specific drug in the drug
class can be identified from an initial screening test. Consequently,
the specimen undergoes confirmatory testing to determine the
specific drug or drugs present in the urine sample. In some
cases, even though a screening test is positive, the confirming
test may be negative. There are several reasons why this could
occur:
- The substance is below the detectable limit of the confirmatory
test.
- There are hundreds of drugs within a certain drug class,
and we only test for the most commonly found substances;
therefore, the subject could have been exposed to a drug
in the class for which we do not run confirmatory tests.
- Cross-reactivity with any number of other substances,
such as herbal remedies, drugs from other classes or harmless
substances, such as poppy seeds.
Regardless of the circumstances, you will most likely need
to await the confirmatory results and consult with your medical
monitor for the ultimate determination as to whether or not
it is acceptable for the subject to continue in the study.
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