I believe they are more sensative than the ones you can buy. When I went to the walk in because I sure I had a bladder infection they did a pg test and it was pos, thing is I couldnt get a hpt to come back pos no matter what kind it was. Are you late for AF? If so how late? I would take a few more days and if it doesnt come I would go to the dr and get some blood work done that is the best way to tell.