Positive results

• the laboratory found evidence of that drug in amounts above the cut-off level, and
• the MRO did not identify a legal and verifiable medical source for that drug.

A Positive - Unable To Contact Donor result means the MRO was unable to contact the donor to grant the opportunity to account for potential medical sources and discuss the donor's rights and options relating to the test result.  The donor should be advised to call the MRO right away.

Quantities and Cut-off Levels

Above are the Cut-off Levels used in Department of Transportation (DOT) regulated tests.  If your tests are Non-DOT, you may have different cut-off levels, and these will be displayed on the result certificates.  You may notice that there are two cut-off levels for each drug: screening and confirmation.  For some drugs, they are the same.  For a few, they are different.  This is because the two tests (screening and confirmation) are very different in their processes.

Screening tests, often called “immunoassay”, use a known chemical reaction to determine if a specimen is likely positive for a drug of interest.  We use terms such as “likely positive” or “presumptive positive” because screening tests are known to sometimes interact with chemicals other than the exact one for which we are testing.  For the most part, those other chemicals are closely related to the drug of interest, and they are also found in the drug of abuse being tested.

When there is a difference between the screening and confirmation cut-off levels, this means that the screening test is likely to react to multiple similar chemical structures, whereas the confirmation test is only detecting a single specific structure.

For example, when testing for marijuana in a DOT-regulated test, the screening test has a cut-off level of 50 ng/mL, but the confirmation testing is only 15 ng/mL.  Sometimes, having learned that his final level was below the 50 ng/mL, a donor will insist that he “should have” passed the screening test.  This is not true.  There are over 60 cannabinoid metabolite structures produced in urine from use of marijuana.  The final quantitative result on marijuana only tells how much of one particular of these, THCA (full name: delta-9-tetrahydrocannabinol-9-carboxylic acid), was detected.  The screening test will pick up on that THCA and several other cannabinoid structures.  It is specifically because the screening test is sensitive to these multiple structures that the cut-off level on the screening test is set higher to begin with.  Under DOT regulations, if a donor's specimen has a confirmation result for THCA above 15 ng/mL, it is a Positive test, and the employer is not permitted to allow that donor to continue safety-sensitive work.
 
If the result of a screening test is above the screening cut-off, the specimen then moves to the confirmation testing stage.  Confirmation testing is done by gas chromatography–mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS).  Put simply, these methods separate the atoms of the substances in the sample and measure the exact amount of a specific chemical structure that is present in the specimen.

Negative results

• drug not present
• the laboratory did not find evidence of that drug in amounts above the cut-off level, or
• the drug was detected by the laboratory, and the MRO determined the drug was likely present due to the donor's use of a medication obtained through a legal and verifiable source.

Cancelled results

If a test is cancelled due to an error on the part of the collector (such as a mismatched Specimen ID number), there would be no reason to suspect the donor of any wrongdoing, and the test would be treated as though it never happened.

If the test is cancelled due to some unusual characteristic of the urine, and a verifiable reason for that characteristic cannot be identified, an observed recollection would be required (in the case of DOT testing) or recommended (in the case of non-DOT testing).  The purpose is to obtain a specimen that is known for a certainty to not have been altered.  For example, if the specimen encounters interference when undergoing the screening test, but the MRO cannot identify a medication that is known to cause interference, this would be a situation where the inability to determine a normal result would justify an observed recollection.

A Cancelled result, even if due to some unusual characteristic in the urine, is not necessarily proof of wrongdoing by the donor.  If any action is required or recommended for a Cancelled test, it will be disclosed in the printed remarks, immediately above the MRO's name and signature on the Specimen Result Certificate.

If the unusual characteristic clearly indicates tampering, the test would not be reported as merely Cancelled.  See the notes under Adulterated Results or Substituted Results below for discussions on tampered specimens.

Adulterated results

An Adulterated result is generally caused by the donor adding something to the urine to interfere with the testing process.  This should be treated with the same consequences as a Positive result.

Substituted results

Often, this is a synthetic urine substitute, apple juice or even plain water.