Quote Originally Posted by 757690 View Post

False positive rates on those tests are significantly lower than your assumptions. Test with that high of a failure rate would never be used at a professional level, since as your logic proves, they would provide way too many cases of innocent people indicted.

I don't know that rates for these tests, but I get tested on a regular basis for certain health issues, and I was warned that these tests, which are similar to the first test, have an error rate of around 1.25%, which, given the frequency of my test, actually is still significant.

So when elevated levels are detected, just like with the drug tests, my doctors do a second round of testing in the same sample, with a different, much more expensive method, just to be sure. That second method, they say, is almost never in error. I was never given a number, but I assume it's a fraction of the 1.25% error rate of th first test.

I have no idea if this is the same numbers with drug testing, but I would think if it was like you said, no union would ever allow it, and no court would ever uphold it's findings.
With the first test, I would note that the 4:1 ratio required to "fail" the test is actually in the "normal" range and not necessarily a sign of having cheated. It merely serves as a filter to limit those who take the more complex/expensive test to whose who are more likely to have been cheating. So you wouldn't even need to have a false positive on the first test -- merely a correct positive that happens to be a natural condition.