rhp1822

I have used the dillution/asprin method 5 times now and it has worked like a charm, but this last time after I pissed he checked it, and told me that I had to come back in the morning and re-test, and not to take any pills, I didnt ask Q's I just left, I was wondering if there is a test to detect asprin or the vitamin B in my system, all he said was to not take anything before my test, does anyone have any Idea what he saw. he used a tester that wasnt a traditional dip-stick it had about 6 round indentations in it, he dipped it in and waited about 3-5 min, and told me to come back, does anyone have any idea what he tested for, and is there any way to combat this? Thanx