Urinalysis (THC) Facts

[Onezie]

A friend recently had a drug test and asked me to help them get some info - I'm better at googling. I found some good source material that people can use to give themselves a realistic estimate on when they will be able to naturally pass a piss test (UA). If you don't know what your next step is hopefully this information will be helpful. First a few basic things:

-The most common pre-employment screen is a 50 ng/mL immunoassay (I/A), basically a dipstick-like test, if non-negative it's followed by a 15 ng/mL (GC/MS) confirmation. The second test is just more expensive and precise, you should have the same probability of passing either one at those cutoffs.

-You have access to your own tests online and at local pharmacies (more expensive) which should be over 99% accurate. Best to avoid dollar store tests. Pharmacy kits can include a verification by GC/MS, if you have the time it's not a bad idea to send in a sample if you want to know your levels more precisely.

It is best to test yourself in the morning, and perhaps if you fail, to test again later in the day when more hydrated to see if you are alternating. One problem is that dipstick tests are very accurate but the faint line result they can produce is somewhat open to interpretation. If you can see a faint line then technically you passed the I/A and no more testing is needed. Even people who've never ingested any form of THC can have fainter lines. The reason it's faint is that the test looks for a tiny concentration of metabolites relative to its precision. HOWEVER, if you see only very little coloration, or perhaps even a "ghost line", then you may actually be close to the cutoff.

The time it takes for the majority of people to consistently pass a UA is actually shorter than most people think. Of course for a smaller group of people it will take longer and even longer for a smaller group and so on... A 2006 review of THC research in the Drug Court Review puts it this way:

"Based upon recent scientific evidence, at the 50 ng/mL cutoff concentration for the detection of cannabinoids in urine (using the currently available laboratory-based screening methods) it would be unlikely for a chronic user to produce a positive urine drug test result for longer than 10 days after the last smoking episode"
"At the 20 ng/mL cutoff concentration ... it would be uncommon for a chronic marijuana smoker to produce a positive urine drug test result longer than 21 days after the last smoking episode."

http://www.ndci.org/sites/default/fi...n_Window_0.pdf

Notice how he said "unlikely", some people will wait longer than that. A 2008 study of THC elimination times showed that people can alternate between passing and failing at the 50 ng/mL I/A for days.

Urinary Elimination of 11-Nor-9-carboxy- 9-tetrahydrocannnabinol in Cannabis Users During Continuously Monitored Abstinence

Of the 60 users in the study, about 71% were able to pass their first test in 5 days or less. The users in the study with higher BMI and normalized THC/creatinine ratio (Cmax, ng/mg) tended to take longer, passing consistently at an average 15.4 days. However, some shortcomings of the study (it only ran a month, some people left after only a week or two) may suggest that the average time for this higher Cmax group could be longer than 15.4 days. They mention that the time it takes until you are under the test cutoff is highly correlated with your initial Cmax and BMI, and yes, likely the self-reported daily usage.

I took my friend's BMI, reported usage, gender, and age and compared them to a group of similar subjects in the study and found that the time to test clean would be around 10 days. They used home tests on day 18 and on the subsequent 4 days, all faint lines, all passing results. They underwent their UA on the 25th day of abstinence and got a non-negative on the 50 I/A screen. A couple days later the lab reported their sample negative (passing), confirmed by GC/MS. It is entirely possible the initial tester mistook a faint line as a fail or that no line actually appeared, but it seems highly unlikely a person would fail if they had been passing consistently a few days earlier. Hopefully this is beneficial to some folks, drug tests can be a stressful experience, especially if it impacts their career and/or family.

*Drug testing laws can vary widely state to state, it may be helpful to look these up and know what rights you have, maybe whether your company even has the right to test you at the time or what you can do if receiving a failing result.*

Onezie Reviewed by Onezie on 10-27-2013. Urinalysis (THC) Facts A friend recently had a drug test and asked me to help them get some info - I'm better at googling. I found some good source material that people can use to give themselves a realistic estimate on when they will be able to naturally pass a piss test (UA). If you don't know what your next step is hopefully this information will be helpful. First a few basic things: -The most common pre-employment screen is a 50 ng/mL immunoassay (I/A), basically a dipstick-like test, if non-negative it's Rating: 5

[swim714]

"At the 20 ng/mL cutoff concentration ... it would be uncommon for a chronic marijuana smoker to produce a positive urine drug test result longer than 21 days after the last smoking episode."

This is helpful, thanks. I am testing negative for the 50 ng/ml cutoff, but I am afraid they might run a GC/MS because I will be testing positive for a prescription medication I am taking. BurntToast seems to know their stuff and I read somewhere else in the forum that they would only do a GC/MS for whatever substance came up positive on the initial test, but I have seen conflicting info elsewhere and am paranoid.

[Burnt Toast]

Thats right. Because of the hefty costs of the GC/MS, Only the drug panel(s) that have tested non-negative on the initial assay screen will undergo the confirmation GC/MS.

And if youre worried about the GC/MS because of its lower (numerically) cutoff threshold, dont be. Even though their cutoff thresholds numerically differ, a 50 ng assay screen is functionally equivalent to the 15 ng GC/MS. For more info, read post #7 of this thread:
http://boards.cannabis.com/drug-test...d-testing.html