Screening – Parent Drug

When looking at an MRO report sometimes understanding all of the line items can be a bit confusing. When a urine test is done at a laboratory there are two possible steps happening in the testing procedure. The first test that will be done on the sample will be a screening test. This test will use immunoassay technology and screen for a particular drug class or parent drug. Often this is called an umbrella test as it will look for anything within that drug class, the parent drug and/or the metabolites, depending on the drug being screened. If the drug is present in the specimen at a threshold at, or higher then the tests cutoff, the test will screen as a non-negative. The screening test is a qualitative result, there is no specific amount for how much of that parent drug and or metabolite(s) are in the sample, it is simply above or below the threshold for that drug’s test. 

A parent drug is the starting compound, meaning the compound that is initially taken in by the individual, before any breakdown by the body. This drug will go through a biotransformation once within the body as the body works to break it down into compounds that can be more easily dissolved into the blood. These compounds that the body breaks the parent drug down into, are called metabolites. This transformation must be done by the body so that the compound can be eliminated from the body, so that it doesn’t just accumulate which would eventually lead to the compound poisoning the body (toxicity). 

In general the metabolites from a compound are less toxic and have less activity on the body then the parent drug. However, as with all things there are exceptions, for example morphine is an active metabolite of the less active parent drug, codeine. In drug testing when the screens are done they are screening for the parent drug or drug class, and if, and only if, that screen is non-negative will they do further confirmation testing with the LC/GC/MS testing, as appropriate for the specimen. 

Confirmation Testing – Metabolites

When the laboratory does confirmation testing they will now be choosing specific metabolites from that parent drug to pinpoint and test for quantitatively, meaning they will produce a number for how much of the metabolite is present within the specimen.

On a drug test this means that if there is no confirmation test required for a certain parent drug/class, you will not see the breakdown of what the metabolites would be that would be confirmed for, should that have been required. This means for something like opiates where the screening test will be looking for opium alkaloids and/or their metabolites, if the test is negative it will simply say Opiates – Negative, however if they had to do a confirmation for opiates, you would also see the breakdown of Codeine and Morphine listed out, as they will then have looked specifically for the parent drug and the metabolite of it, to pinpoint quantitative results for either/both.

Some example of drugs which have this parent drug/drug class screen with a breakdown for confirmation tests includes:

  • Opiates screen – codeine / morphine confirm
  • Amphetamines screen – amphetamine/methamphetamine confirm 
  • Cocaines screen – cocaine/benzoylecgonine confirm 
  • Hydrocodone screen – hydromorphone/hydrocodone confirm  
  • Oxycodone screen – oxycodone/oxymorphone confirm

This means that for each of those pairings listed above, if the screen is negative you will not see the metabolite even listed on the report. However, if it was positive you will see both line items, ie Opiates and Codeine listed on the MRO report. Often the MRO will tidy up the report to remove what seems like a repetition of the parent drug as a line item, however this is not always done. Now you will understand that if you see Amphetamine listed twice, like in the example below, the first line item is reflective of the screen for the drug class, and the second two line items are the confirmation tests looking for each of those items specifically. Cocaine is also shown here in this example, with the first line being the parent drug Cocaine listed, and then the confirmation test being done for the Cocaine Metabolite (Benzoylecgonine) shown as a second line item underneath it, both showing as positive. As well you can see that neither oxymorphone, nor hydromorphone are even in the list, as their parent drugs did not screen positive so no breakdown to confirm metabolites was required.

Obviously this would be different if you were sending a specimen to the lab asking for a Confirmation test for a specific metabolite. For example if you sent a request for a confirmation test for Methamphetamine or Hydrocodone, in that case the metabolite would be listed alone as a line item, as it would be just a confirmatory test that was run, bypassing the screen all together.