IF this is a false positive, I land on 85% because only 85% of people who test with index values of 1.1 to 1.5 confirm with western blot when four months have passed since a concerning encounter, such as yours. The percentage that does not confirm with western blot increases as the index value get closer to 3.5. In total, 50% of people who test between 1.1 and 3.5 do not confirm with western blot.
Terri