Marijuana Detection Time Shorter Than Previously Assumed

Discussion in 'Drug Testing' started by Motorhead, Feb 24, 2006.

  1. Motorhead

    Motorhead Platinum Member & Advisor

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    Marijuana Detection Time Shorter Than Previously Assumed

    February 23, 2006 - Columbia, MO, USA

    Columbia, MO: The length of time cannabis metabolites may be detected, on average, on a standard urine screen is typically no longer than ten days for chronic users and between 3-4 days for infrequent users, according to a literature review published in the current issue of the journal Drug Court Review.
    "Recent scientific literature indicates that it is uncommon for occasional marijuana smokers to test positive for cannabinoid [metabolites] in urine for longer than seven days" at 20 ng/ml or above on the EMIT (Enzyme Multiplied Immunoassay Technique) test, the author concludes. "Following smoking cessation, chronic smokers would not be expected to remain positive for longer than 21 days, even when using the 20 ng/ml cannabinoid cutoff."
    When tested at the 50 ng/ml cutoff threshold, infrequent users typically test negative for the presence of marijuana metabolites within 3-4 days, while heavy users typically test negative by ten days after ceasing use, the study found.
    While several clinical trials from the 1980's found cannabis metabolites to be identifiable in the urine at low concentrations for longer periods of time, particularly in heavy users, the author suggests that more advanced drug-testing technology has narrowed this window of detection.
    "As cannabinoid screening tests evolved, these improved assays became more selective in the manner in which they detected marijuana metabolites," the author writes. "As detection specificity increased, the length of time cannabinoids were being detected in urine decreased. ... Therefore, the results of cannabinoid elimination investigations performed in the 1980's may no longer be applicable to estimating the detection window for marijuana in urine using today┬╣s testing methodologies."
    After reviewing data from more recent clinical investigations of chronic marijuana smokers, the author reports that the "average detection window for cannabinoids in urine at the lowest cutoff concentration of 20 ng/ml was just 14 days." However, the author also notes that a minority of subjects continue to test positive for cannabis metabolites after 28 days, even when tested by more advanced drug-testing technology.
    Approximately 55 million drug screens are performed annually in the United States. The majority of these are workplace urinalysis tests, which detect the presence of drug metabolites (inert byproducts produced after a substance is metabolized by the body), but not the substance itself. Consequently, the US Department of Justice affirms that a positive drug test result for the presence of a drug metabolite "does not indicate ... recency, frequency, or amount of use; or impairment."
    For more information, please contact Paul Armentano, NORML Senior Policy Analyst, at (202) 483-5500. Full text of the study, "The marijuana detection window: Determining the length of time cannabinoids will remain detectable in urine following smoking," is available online at: http://www.ncdi.org/ndcirpub.html

    The link to ncdi doesnt work tonight for some reason.
     
    Last edited by a moderator: Sep 10, 2017
  2. melt_000

    melt_000 Newbie

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    i don't understand. they improved the test by making it less accurate? i guess it's okay with me..
     
  3. Motorhead

    Motorhead Platinum Member & Advisor

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    Yes the wording is a little confusing. ncdi.org must be having server problems because i couldnt even get the home page to open to look for the full text myself.
    Basically what they are saying is that EMIT is the worst kind of test out there, however it is the most commonly used because it is the cheapest. It uses enzymes to detect metabolites, not necessarly the drug itself, in your urine. While the drug may be long gone metabolites may still remain and thus you get a postive reading. I think that is quickest way to explain it. Somebody help me out if im not totally correct.
     
    Last edited: Feb 25, 2006
  4. goslamsomeTHC

    goslamsomeTHC Newbie

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    i knew it, because i am a moderate to heavy smoker and was randomly drug tested once, i had 3 days notice so in those 3 days i did not smoke, bam passed my test, but i did drink a crap load of water about 1 1/2 hrs before the test to help dilute it, lol.
     
  5. Motorhead

    Motorhead Platinum Member & Advisor

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    The link i posted last night was a commericial site, like most of them with drug testing info. So I found this little pdf with a good explaination of the process. It is in the file archive here: Marijuana
     
    Last edited: Feb 26, 2006
  6. Richard_smoker

    Richard_smoker Gold Member

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    They made the test more specific. Specificity and Sensitivity are two totally different ends of the spectrum. Sensitive tests will give you false positives. NO ONE wants to accuse someone of doing drugs when they really didn't! So, yes, the test is better because it is more specific to the canabinoid metabolites. And it also can be less sensitive now because the tests are so specific. so, less false positives, more true positives.
     
  7. melt_000

    melt_000 Newbie

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    yeah i thought bout that, but that would mean all the old tests that were positive at like 3 months were actually false positives.
    and if marijuana smokers after 10 days (or 30) have the same chance of testing positive as someone who didn't smoke marijuana at all, how did they get the figure of 3 months maximum?
     
  8. sands of time

    sands of time Gold Member

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    So is this test actually testing for THC itself? From what I recall, the current piss tests that are so widely used test for the substance that THC is metabolized in.
     
  9. Motorhead

    Motorhead Platinum Member & Advisor

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    Urine tests look for the drug itself or metabolites. The longer the drug is in your system the more degraded it will become. It is the detection of these specific metabolites that has improved since the 80's, and they are finding that the time that these specific metabolites are in your urine is alot less than previously assumed.

    Quote:
    In drug testing, a false positive is defined as a drug free sample falsely being reported as showing positive for drugs. This can occur for a number of reasons including: improper laboratory procedure, mixing up samples, incorrect paperwork and passive inhalation. But the most common cause of drug testing false positives are cross reactants. A cross reactant is a substance which because of its similar chemical structure to a drug or its metabolite can cause a false positive result.

    Basically, they have gotten better at deciphering cross reactants(improved specificity), thus less false positives.

    Some more general info:
    Urine Drug Testing

    The following is a summary of the analytical methods used by laboratories to detect the presence of drugs or their metabolites in urine.
    Immunoassays

    These tests are most commonly used to screen samples. In the event that drugs or their metabolites are detected, then the sample is normally tested again using an even more sensitive test such as Gas Chromatography and Mass Spectometry. Immunoassays work on the principle of antigen-antibody interaction. Antibodies are chosen which will bind selectively to drugs or their metabolites. The binding is then detected using either enzymes, radioisotopes or fluorescent compounds.
    EMIT (Enzyme Multiplied Immunoassay Technique) is manufactured by Syva Laboratories. It uses an enzyme as the detection mechanism. It is the cheapest, simplest to perform and the most widely used of the immunoassays. Unfortunately, it is also the easiest to fail and more worryingly, the least accurate: giving a
    4-34% false positive rate.
    RIA (Radio Immunoassay) is manufactured by Roche Diagnostics. It is similar to EMIT but uses a radioactive isotope such as iodine instead of an enzyme. However, because it involves using radioactive substances, it is less popular than EMIT. This is a highly sensitive form of testing mainly used by the military.
    FPI (Fluorescence Polarization Immunoassay) is manufactured by Abbott Laboratories. Fluorescent compounds mark the selective binding of antibodies to drugs and their metabolites. It is highly sensitive and highly specific.
    Thin Layer Chromatography

    This procedure involves the addition of a solvent to the sample causing the drugs and their metabolites to travel up a porous strip leaving colour spots behind. As each different substance travels a specific distance, the strip can then be compared with known standards. This test gives no quantitive information, it merely indicates the presence of drugs or their metabolites. Furthermore, it relies on the subjective judgement of a technician and requires considerable skill and training. It is not widely used.
    Gas Chromatography and Mass Spectometry

    These are the most precise tests for identifying and quantifying drugs or their metabolites in the urine. They are usually used as a confirmation test following a positive result on an Immunoassay. It involves a two step process, whereby Gas Chromatography separates the sample into its constituent parts and Mass Spectometry identifies the exact molecular structure of the compounds. The combination of Gas Chromatography and Mass Spectometry is considered to be the definitive method of establishing the presence of drugs or their metabolites in the urine. However, the equipment necessary to perform it is extremely expensive and this is reflected in the price for testing each sample. Occasionally problems do arise with poor calibration of the equipment.

    Im still ticked about that broken link though. I should have checked it out before I posted it.:crazy
    cheers