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What Does a Non-negative Drug Result Mean?

A non-negative result is a collective term that essentially refers to any test that is not negative. In other words, the test cannot accurately determine that no drugs are present in the testing subject’s urine, hair, or oral fluid sample. Specifically, federal drug testing rules for urine drug testing categorize a result as non-negative if the test result for the specimen is adulterated, substituted, or invalid. For example, a specimen may be categorized as non-negative if the test indicates that the specimen has been diluted or adulterated. In these instances, tampering may prevent the specimen from testing positive for the targeted drug but cannot rule out the possibility of drug use by the test subject.

What happens after someone received a non-negative result?

It is critical to understand that a non-negative test result does not imply that the test was negative or positive. What happens following a non-negative drug test result depends on the employer’s drug and alcohol policy. In most cases, a non-negative test will be required to be sent to the laboratory for confirmation testing. Employers will suspend worker duties, particularly anything safety-sensitive, until confirmation testing results are available.

Why is confirmation testing needed?

Any instant drug screen, whether the sample is oral fluid or urine, is the most cost-effective way to rapidly detect the presence or absence of a drug or its metabolites. This is an important first step and is a much quicker and cheaper option than simply sending all biological samples to the laboratory for testing.

A non-negative result requires confirmation testing from the laboratory to determine exactly what drug was taken and the quantity present. GC-MS can screen for hundreds of different drugs. Unlike other types of urine tests, such as an immunoassay (IA), it can detect the presence of both specific drugs and their metabolites.

In summary, under the standards that guide workplace drug and alcohol testing, results are defined as one of the following three testing outcomes:

Negative. This means the testing did not detect the presence of a targeted drug or its metabolite in the sample.
Non-negative. This is an initial positive result obtained using a screening device, which is then subject to confirmatory testing by the laboratory.
Positive. This is where a non-negative screening result has been subsequently confirmed positive by a testing laboratory or a medical review officer.

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