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-   -   What can cause a negative result on a drug screen when someone has taken the drug? (https://www.askmehelpdesk.com/showthread.php?t=672682)

  • Jun 19, 2012, 06:22 AM
    ML77
    What can cause a negative result on a drug screen when someone has taken the drug?
    Recently had negative results on a drug screen that I know the person has taken the drug. How can that be?
  • Jun 19, 2012, 06:37 AM
    DrBill100
    Quote:

    Originally Posted by ML77 View Post
    Recently had negative results on a drug screen that I know the person has taken the drug. How can that be?

    The reasons are too numerous to outline. False negatives occur in 10-40 % of drug screens largely dependent on the manufacturer, testing facility and specific drug tested for. The underlying cause is the two-tiered approach to drug testing utilized by laboratories paired with requesting party failing to specify test parameters. What type of drug do you believe was missed?
  • Jun 19, 2012, 01:19 PM
    ML77
    The drug was Hydrocodone. The test was done at a professional lab.
  • Jun 19, 2012, 01:31 PM
    DrBill100
    Quote:

    Originally Posted by ML77 View Post
    The drug was Hydrocodone. The test was done at a professional lab.

    Detection of Hydrocodone requires a specific test. It would not be picked up on the standard opiate panel. It is easy to miss even when specifically tested for unless the test is ordered for "Level of Detection" (LOD), which means the instrument is set to the lowest possible setting.

    The above requires a test by GC/MS and not simply a drug screen by immunoassay (IA).

    Laboratories use standard screening protocol unless advised otherwise. Where it was performed is of far less consequence that what was performed.

    If you have a printout or test order we can determine the test performed.
  • Jun 19, 2012, 09:04 PM
    ML77
    As far as I know it was just a standard test. I don't have a printout or copy of order.

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