[Focault's Pendulum]

That isn’t how the tests are performed. Periodically a test will generate a positive where it hasn’t in the past for a lot of different reasons. False positives are inherent to the system, just as false negatives are

I tested positive for a controlled narcotic. I take a beta blocker. How could you get a false positive from that?

[ican'tbelieveit]

The test procedures malfunction from time to time. I just had some data I generated a couple of years ago questioned. The submitter resubmitted material pulled at the same time and stored since then. One result was confirmed, another was not confirmed. So, when I tested two years ago, I showed twice that the results were the same, but now it doesn’t show up. Why? The vial the sample was stored in was contaminated? I don’t know. It happens.