Tisa and I had been dating for about 4 months when she signed up to participate in a clinical study for wisdom tooth removal. Basically it was one of those deals whereby they pay for all of your expenses in exchange for you testing out new post-operative pain medications. Of course you always run the risk of being in the placebo group or having the medicine not work (or worse, work adversely), but of course the cost of not having to pay for wisdom tooth removal makes it highly worthwhile.
Anyway, I woke up very early one Saturday morning so that I could take Tisa to the clinic around 38th street and Kerbey Lane so that she could get on with the procedure. It was probably around 6:30 in the morning that I dropped her off. I drove back home, got into bed, and quickly fell asleep. It probably wasn't more than forty minutes later that I was awoken by my phone. It was Tisa and she needed me to come and pick her up at the clinic. I asked her what was wrong and she said we would talk about it later.
I was very concerned at this point, and worse was that I was exhausted and had a summer school final to take later in the afternoon.
I went and picked her up at the clinic and as we started to drive home, I asked her what had gone wrong. She told me she had failed the obligatory pregnancy test that they give everyone. Naturally my heart stopped beating. I'm not sure how long it took to resume normal function.
After some brief period of time, she exclaimed to me that she was not pregnant. At least not that she knew of. I was utterly confused.
A couple of weeks prior, Tisa had been out with some of her friends and at some point a little pot-smoking may have occurred. The clinical studies are very specific in that you can't have any type of prior drug intake to participate. Of course most rational people recognize that smoking pot weeks earlier is not going to alter the chemistry of a pain narcotic weeks after the fact, but that's how they operate.
Evidently when Tisa went into the bathroom to fill her urine sample for both a pregnancy AND drug test, there was a bottle of apple juice sitting atop the toilet. Although we argued about it quite extensively, I contended it was just accidentally left there by someone else, but she swore that it was specifically there so that people had "something else to use". Whatever the case, she did in fact use the apple juice. She mixed some of the apple juice with warm water and turned that into the doctor for her test.
So the punchline to this entire story is that I have no idea how this happened, why it happened, or if it is in any way scientifically relevant, but evidently a watered down apple juice can alter the chemistry of a clinical pregnancy test to show a false positive.