GC/MS interference for drug taken by donor

GC/MS interference for drug taken by donor

Postby asolanomd » Tue Jul 27, 2010 12:23 pm

I received a drug test report of a non-federal 10-panel that was confirmation-negative for everything except benzodiazipines. Next to benzodiazepines it had the comment, "alpha- hydroxyalprazolam - interference by GC/MS." When I spoke to the certifying scientist it was explained to me that there was a peak in the area expected for alprazolam but they couldn't quantify a level because of some interference. They couldn't say if the interference was possibly due to antibiotic or anti-inflammatory drug use. In interviewing the donor, he does admit to having a prescription for Xanax 1 mg and will have the pharmacy fax me documentation. He states that he is also on a BP med and Ultracet but has not been on any OTC Motrin or antibiotics. As previously mentioned, the other 9 test components in this panel are negative. If his explanation, including his documentation is valid, would this test be ruled negative or should it still be cancelled and immediate recollection under direct observation?
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Re: GC/MS interference for drug taken by donor

Postby DrSteve » Tue Jul 27, 2010 3:09 pm

asolanomd wrote:I received a drug test report of a non-federal 10-panel that was confirmation-negative for everything except benzodiazipines. Next to benzodiazepines it had the comment, "alpha- hydroxyalprazolam - interference by GC/MS." When I spoke to the certifying scientist it was explained to me that there was a peak in the area expected for alprazolam but they couldn't quantify a level because of some interference. They couldn't say if the interference was possibly due to antibiotic or anti-inflammatory drug use. In interviewing the donor, he does admit to having a prescription for Xanax 1 mg and will have the pharmacy fax me documentation. He states that he is also on a BP med and Ultracet but has not been on any OTC Motrin or antibiotics. As previously mentioned, the other 9 test components in this panel are negative. If his explanation, including his documentation is valid, would this test be ruled negative or should it still be canceled and immediate recollection under direct observation?



It appears that the lab should be reporting this result out as an "Invalid, GC/MS Interference". Based on your post and your interview, and using federal regulations, this would be a verified final result by you, the MRO, as "Test Canceled." The donor would then need a second observed collection as you stated. Even though this is not a federally regulated test, most MROs do our best to follow federal guidelines for all tests. An argument could be made for this particular test going another direction, but I do my best to follow Part 40, and federal regulations, for both regulated and nonregulated tests.
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Re: GC/MS interference for drug taken by donor

Postby gwoccmed » Tue Jul 27, 2010 8:12 pm

While following the regulations is always defensible even on non-regulated, I have a slightly different approach for this non-regulated test. The lab verified negative the all but the alprazolam which was invalid (as a positive) because they couldn't get a stable quantification. Your donor can account for its presence but not the interference which now becomes moot. I'd save everyone a lot a trouble and simply call it negative. I also wouldn't lose any sleep over the idea of defending this as a negative in the extremely unlikely event of a challenge.
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Re: GC/MS interference for drug taken by donor

Postby DrSteve » Wed Jul 28, 2010 12:46 pm

gwoccmed wrote:While following the regulations is always defensible even on non-regulated, I have a slightly different approach for this non-regulated test. The lab verified negative the all but the alprazolam which was invalid (as a positive) because they couldn't get a stable quantification. Your donor can account for its presence but not the interference which now becomes moot. I'd save everyone a lot a trouble and simply call it negative. I also wouldn't lose any sleep over the idea of defending this as a negative in the extremely unlikely event of a challenge.


Agreed. You are not going to get a lot of questions after releasing a negative result! And assuming what was posted is accurate and not omitting anything, I might have also gone that route as well.
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Re: GC/MS interference for drug taken by donor

Postby asolanomd » Wed Jul 28, 2010 1:55 pm

Yes what was posted by me is correct and I received faxed validation for Xanax.
I will go ahead and verify as negative.
Thanks
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