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Drug Metabolite Levels--leave them to the pros
By Steve Barber

One of the occupational hazards of working with drug screens is the possibility of making wrong decisions based on a misunderstanding of the underlying science. Take, for example, the issue of drug metabolite levels in positive drug screens. I deal with questions about this on an almost daily basis.

Just yesterday, a client asked to review the levels of a positive marijuana screen. When I asked her why she wanted that information, she responded, "He tested positive six weeks ago. I just wanted to make sure the levels were going down."
Here are the problems with that approach:

  1. Marijuana is detectable in the urine for a maximum of 30 days in chronic users. For occasional users, that detection window is even smaller--1 to 3 days.
  2. Reduced levels are no guarantee of abstention.
  3. Levels can actually increase with no concurrent drug ingestion, as the relative concentration of the urine changes.
  4. High levels are not reliable indicators of heavy use; low levels are not reliable indicators of minimal use.
  5. Non-physicians are not qualified to make judgments based on levels for anything other than "positive" or "negative."

Why you should avoid making decisions based on metabolite levels
Many factors influence metabolite levels. The donor's weight, metabolism, the amount of substance actually ingested, the length of time since ingestion, and the relative concentration of the donor's urine at the time of collection are among them. The only people qualified to make judgments about the metabolite levels are physicians--specifically, physicians who have undergone additional training and certification to become Medical Review Officers (MROs).

But what if you have concerns that a client is abusing or overusing his prescribed drug? Again, that is a question for the pros. A Medical Review Officer can review the results, including levels, review your client's prescription and even talk with your client and/or your client's prescribing physician. Then, he or she can make an informed decision that you can count on.
 If you make life-changing decisions about clients, defendants or job candidates, you really cannot run the risk of making a wrong decision based on a faulty understanding of drug screen results. Not only could a wrong decision adversely affect the donor's life, it could ultimately result in litigation directed at you or your organization.

To avoid this, Span advises our clients to use Medical Review Officers for any and all positive drug screens.
Be smart. Leave it to the pros.

© copyright 2008 Span Corporation

Steve Barber is Director of Testing Service for Span Corporation, a national provider of drug screen and background investigation Third Party Administration services. Span Corporation headquarters are located at 1505 White St Ann Arbor MI 48103. Mike, Steve and Span Corporation can be reached at 734-623-7726 or Website URL:

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