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What is the difference between third generation and fourth generation HIV test?

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General Surgeon
Practicing since : 2008
Answered : 1290 Questions
1.) What's the earliest a person can take a 3rd generation hiv test after havin unprotected sex & get a 95% accuracy rate?? 2.) What would the accuracy rate be at 25 days & at 27 days after havin unprotected sex? 3.) What's the differance between a 3rd & 4th generation hiv testing at 27 day after havin unprotected sex??
Posted Tue, 18 Feb 2014 in HIV and AIDS
Answered by Dr. Ashish Verma 4 hours later
Brief Answer: 3 months for 3rd gen, 1 month for 4th gen Detailed Answer: Hi, Thanks for writing to XXXXXXX This is Dr. Ashish Verma, a general surgeon, answering to your query. I will be answering in sequence wise as you had asked them: 1) To get a 95% accuracy witha 3rd geneneration hiv test, you have to wait for atlest 3 months, as the test detects antibodies, with takes about 3 months to show in blood. 2) the aauracy rate at 25-27 days will depend upon the type of test performed. Using a 4th generation test at this time will give you almost a 100% accurate results. But a third generation test will have a low accuracy. 3) 4th generation test has a window period of 11 days to 1 month, so at 27 days, their accuracy will be almost 100%. And as explained earlier, the window period of 3rd gen test is 3 months, so their accuracy will be quiet low at this period. Hope, that i have answered to all your queries. If you have further queries, i will be glad to answer them. Regards, Dr. Ashish Verma
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Follow-up: What is the difference between third generation and fourth generation HIV test? 1 hour later
I was told by another doctor on this site that at 27 days the accuracy of a 3rd generation hiv test would be 95%... Furthermore, your body would start producing antibodies if infected by 20 days and beyond... Not sure which doctor to believe but I'm very nervous.. I took a hiv test at 25 & 27 days after having unprotected sex and it came back negative.. Really nervous about taking another 1...
Answered by Dr. Ashish Verma 1 hour later
Brief Answer: the accuracy at that time will be 90% Detailed Answer: Hi, Sorry for the discrepancies in the answers. Actually for third generation test: 90% people test positive in 4 weeks, 95% people test positive in 6 weeks, and 99.9% people test positive at 3 months, if they are infected. It does takes, about 3 weeks (20-22 days) for the body to start producing antibodies, to for them to reach to a detectable level it takes a few weeks more. But there is considerable person to person variation, and also depends upon the level of viral load in the source. I would suggest that you repeat the test after two weeks, if you are using 3rd gen tests. if you have tested with a 4th gen test at 27 days, and its negative, then there is no reason to worry. Regards, Dr. Ashish Verma
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