I've often heard of women "testing out the trigger" shot - peeing on sticks from the beginning so that when they start testing after transfer, they can be sure it's their bodies producing the hCG, and not the shot they took to ripen their eggs.
I hadn't done this previously. With my first IUI, I waited until 10 days after the trigger shot to test (so, 10 DPO). I got a faint line on FRER that stayed the same color for a day before fading. I never knew if it was picking up the last traces of the trigger shot or if I had a chemical. The same thing happened with my second IUI but not the third; I never had faint positives with my IVFs.
So this morning, I captured my FMU in a disposable plastic cup, then dipped a Wondfo strip in it. Three minutes later, I didn't see anything. I literally took my trigger shot three days prior; there's no way it was out of my system yet. I passed the five-minute mark and only just started to see a hint of something, but honestly? If I'd take a picture you wouldn't have been able to see anything.
It wasn't until the stick was dry that I saw an actual line. Even then, it looked more like an indent evap than a positive test. I even did a second stick in the same FMU to see if it was just a bad one, but no. Same result.
I'm actually kind of glad I did that. I know not to put too much stock in Wondfo negatives now.
(If you come to this post through Google, here's the info on my particular batch: Lot W00130460-3 Exp: 04/2015.)