The Role of Confirmation Testing

Urine drug screening is an effective tool to rule out the presence of drugs in the donor’s sample.  Drug screening technology provides a reliable, rapid and inexpensive means of ruling out drug abuse.

The most common drug screens are immunoassays.  Immunoassays employ a concept that is similar to a vaccination.  The test drug is an “antigen”, in this scenario it is similar to a virus.  The test reagent includes an “antibody”, this is similar to the antibodies produced by our body when injected with an antiviral vaccine.  If drug is present in the sample, it reacts with the antibody.  This reaction is measured and reported as a positive drug screen.

The reliability of a urine drug screen is at least 97%.   One factor that may cause a “false” positive result includes “look alike” drugs.  The amphetamines are the class of compounds that are most at risk for this issue.

The immunoassay used by Ammon Analytical Laboratory detects amphetamine, methamphetamine and MDMA (“Ecstasy”).  High amounts of chemically similar compounds may cross-react and cause a positive Amphetamines assay. Amphetamine-like drugs include ephedrine, pseudoephedrine, and phenylpropanolamine (PPA).  Confirmation testing rules out “false” positives.

The role of confirmation testing is to provide an alternate scientific method that positively identifies the drug(s).  The most common confirmation method is GC-MS (gas chromatography-mass spectrometry).  GC-MS provides a positive identification of the drug; it gives information about the drug’s chemical structure.  The reliability of GC-MS is at least 99%. GC-MS identification is analogous to a “fingerprint” of the drug’s chemical structure.

Some drug screens detect a class of compounds, such as, opiates, benzodiazepines, and barbiturates. There are as many as six or more compounds in each of the noted drug classes.  Many donors provide a prescription when confronted by a positive drug screen result.

 “The positive Benzodiazepines screen was due to the Klonopin I take.”

When GC-MS was performed, it was learned that the result was actually due to Xanax.  The strength of GC-MS includes the ability to identify the different substances that make up a drug class.  Similar scenarios can be imagined for the other classes of compounds.

When the consequences of a positive drug screen are severe, such as incarceration or child welfare issues,  confirmation testing must be considered.  The positive result must be as reliable as possible, i.e. beyond a shadow of a doubt.

If you have any further questions or need to discuss how to request a confirmation test, please contact one of Ammon Analytical’s professional staff at 866-857-8378.

Post Written by: Jerry Meenan

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