Here is a quote from one of FBR's posts, it's in the thread about passing for three days and failing on the fourth day. Read that whole thread it has a lot of good info.

This is the part that explains the reason to take aspirin...
"If you are close to passing but a little over the cutoff taking aspirin can interfer with one brand of immunoassay(the first half of a lab test) test, EMIT. You can't know which brand the lab is using so you take it anyway because it can't hurt."
-Quote from FakeBoobsRule