[Question #275] About the RNA TMA and 4th generation

36 months ago
Hi Drs I have a few question regarding accuracy of the RNA TMA and 4th generation HIV tests. The RNA from what I understand is FDA approved early HIV test. How does it compare to the RNA PCR? I've been told after 11 days it is considered 97-99% after 28 days it is considered 99% what are your thoughts on the accuracy of the RNA TMA. Second is I've heard conflicting info on regards to a second window period of 4th generation testing. Some say there's a time when neither Antigen or antibody can b detected. What are your opinions on this? Third would you consider labcorp testing company a good company to test through?
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
36 months ago
Welcome to the forum.

This question sounds like you're probably trying to make your own decisions about what test(s) to order online. I strongly recommend against it. See a doctor and get professional advice instead. The only legitimate use for either RNA or DNA testing is if there are symptoms that suggest a new HIV infection (as well as an exposure of sufficient risk to make it likely) -- and in that case you need professional care in person. Nobody uses either RNA or DNA testing any more in any situations of lower risk than that. If it's just a question of exposure and you want reassurance, the proper test is a 4th generation antibody/antigen ("duo") test, which can be done at around 10 days after exposure and again at 4 weeks.

That said, my understanding is that the RNA and DNA tests are pretty much identical. The statistics you quote have little meaning in reality. They are what studies by the manufacturer showed, but not necessarily all that accurate. And in any case duo is considered equally accurate as RNA/DNA testing combined with antibody testing. (For sure RNA/DNA testing should never be done alone, without antibody.) In any case, the need for RNA or DNA testing is so rare that I have no personal experience with either of them.

There is no such thing as a "second window" with 4th generation testing. If HIV infection has occurred, either HIV antibody or antigen will ALWAYS be present, usually within 10 days and always within a month. The test NEVER becomes positive then negative and positive again. Those who say such things are not citing data but an assumption based on a misunderstanding of the test. HIV antigen and antibody are not independent. It is the antibody that clears p24 antigen from the blood. For a time both may be present -- but when p24 antigen becomes negative, antibody must be present.

All labs succeed in business only if they provide accurate testing. The two large national lab companies, Labcorp and Quest, are high quality operations with excellent reliability. But as I said, you shouldn't be deciding any of this on your own anyway. Please do it right and see a doctor.

I hope this has helped. Best wishes--  HHH, MD


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36 months ago
Thanks Dr Handsfield unfortunately where I live in the US my doctor or lab don't provide the 4th gen duo only 3rd generation which I took at 12 weeks post sexual Exposure ( receptive anal with someone of unknown status). So I went through LabCorp and took 4th gen duo at 40 days 60 days and 72 days post exposure. I realize my test results are conclusive but all the stress and anxiety are causing me to question my results. Thinking I might be one of the rare cases that doesn't developed antibodies. I've never taken drugs or have any immune problems that I know of.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
36 months ago
Thanks for the clarifications.

"Rare cases that doesn't developed antibodies" are an urban myth. To the extent it happens, it would only be in people with such profound immune deficiency that they would have been ill their entire lives and often dead by age 20. You are correct that your test results were conclusive; all test done more than 28 or more days after the exposure were superfluous. 

For the future, you should understand that any doctor can order any test. Your doctor's office probably uses a particular contract lab, and has decided to use certain tests routinely but not others. However, they can order any test in that lab's portfolio any time they want to do it.

Having said all that, you probably understand that receptive anal sex with a male partner of unknown HIV status is just about the highest risk sexual exposure there is. You weren't infected, but I trust it will be a lesson learned for you. Have condoms handy and use them in settings conducive to temptation; and even then, also ask about HIV status and avoid partners who are positive (and not on treatment), don't know, or seem evasive about it.

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36 months ago
Thanks Dr Handsfield You and Dr Hook are truly amazing. I'll move on from this experience and never do this again Thank you for your expertise.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
35 months ago
Thanks for the thanks. Best wishes to you.


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