Home Test Question

Hello All and Good Morning (at least where I am)..LOL
My brother has been clean for 23 days and 2 days ago he took a home test and it was positive. Last night he comes home, checks mail and a 23 hr notice for probabtion is in the mail. He goes to CVS and get's a home test and it comes back negative (from the instructions it said a faint line is considered a negative). What are the chances that he cleared out withing 24 hrs? Also, the test were not the same type. Anyone have this happen and if so, when you went and actually took your UA...did you pass?

It could have been because he did the test differently. Did he piss a few times before the test? Did he drink lots of fluid? Did he take a mid stream of his piss? Was there a faint line on the thc strip that he didn't see?