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Comment by maze-le | Hacker News Reader

I don't know about THC, but I've been tested positively for Amphetamine before and didn't take it or any medication that is a structural derivate of it. This is a problem that is not very well known, even doctors rarely know how unreliable drug tests can be. Amphetamine-derivates for example have one of the highest percentage of false positives: ~15% -- a lot of molecules in your body have a structural similiarity with the metabolites of the substance.

If you are ever tested positively for an Amphetamine-like substance, and you know you didn't take it -- you should insist on a second test right there on the spot.

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People test positive for all sorts of amphetamines because the test is a joke, overly broad, and unreliable to boot as you pointed out. Anyone who has asthma-related medication is a lock to fail, especially if they take pills like Bronkaid.

Is it because of the ephedrine in the bronkaid that causes the test failures?

There are many types of drug tests. Rapid tests are not super reliable. Lab tests are. We call expert witnesses that do lab tests of urine samples as witnesses all the time... over a multi-decade career, one of our main lab supervisors has overseen the testing of 2 million+ UAs, and they have had one proven error that was due to faulty calibration of an instrument. I would love to see contrary evidence.

The problem is that you’re disqualifying people from jobs for the equivalent of being drunk up to 3 months ago, which is ridiculous. The other drugs that are tested had to have been consumed within the week, because their half-lives are much shorter.

I am definitely not contesting that the drug/work policy in the US is heinous - I fully agree. As long as a person is safely doing their job they should be free to recreate however they see fit. I just think urine analysis lab testing is far more accurate than many people believe it is. I have never even seen a rapid test be wrong once it was sent to a lab, and I have probably seen 200+ such confirmations.

You do have a bit of an availability bias though, since (I assume) only a non-random subset of samples will be sent to a more thorough lab.

Could you clarify which substances you have confirmed? Maybe some tests are better than others.

Marijuana, methamphetamines, and heroine are the three we see the most of. Without a huge essay it is hard to explain which UAs get retested... but in my area of work all positive rapid tests are retested, regardless of if the person is contesting the validity of the UA. A rapid test is obviously a quick test; in my job it is an initial test done by probation officers for probationers. Since these are not “thorough” tests they are always lab tested if they are positive for any illicit substance. Then retested if someone contests the validity of the lab result.

And to clarify, I do not do any testing... I just call witnesses at hearings and trials and review way more UA results than I would like to.

That makes a lot of sense actually. The Methyl group attached to the amphetamine molecule prevents the liver from breaking it down as fast which is why it is more potent and longer lasting in your system. I'm also willing to bet that cocaine is relatively low compared to what one might expect because it's highly water soluble and rapidly degrades.

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