The 3 months test is actually looking for antibodies...Average people can have detected antibodies by 25-28 days..and 99% of the people by 6 weeks...This is the elisa test and is usually recommend for hiv screening..the window period of 3 months is actually very conservative...because people that have immune problems like cancer patients or IV drug users takes slightly longer than 6 weeks to produce antibodies..some states in US and WHO are using 6 weeks for elisa test..some countries like brazil, france, sweden and italy are using 8 weeks as the window period..The 6 months thing is completely outdated liao except for those that kanna needle stick injuries and those on PEP..Anti viral meds 72 hours after protential exposure..to kill off the virus before it spread..The 28 days test is call PCR dna or rna..it detects the actual virus instead of antibodies so 28 days neg is almost gurantee not infected...But this test is damn expensive $380 and it has a 1-2 % false positive...Imagine a person kanna a false positive but he is not infected..the virus haven kill him he already died of heart attack liao..


PS: 12 weeks window period

http://www.thebody.com/Forums/AIDS/S...g/Q146493.html