I wonder what the blood donation uses for testing of hiv. because if it uses the antibody test or duo test, thats not enough for screening hiv in blood because of window period. I heard it uses nat test or pcr test to screen the blood, is that true ?. what is the difference of NAT test and PCR test ?. and when we use pcr test and the result is negative even though we are still in window period, does it mean we are hiv negative ?.