« Go Back

4th Generation DUO test - Window Period

Question: 

Hello and thank you in advance.
Please could you give me some information in regards to the 4th Generation EIA (DUO).
Possible Exposures
1 – Random Northern European girl on a night out she performed unprotected oral then brief unprotected vaginal penetration (less than a minute) then she performed unprotected oral again I did not ejaculate.
2 –Random Bulgarian girl on a night out all protected oral and vaginal penetration. Although protected I’m concerned as she seemed a bit unstable after the event as if she should have had intercourse.
I initially had a duo test after two possible exposures the test came back Reactive negative (14 days & 34 days from possible exposure). I was told to come into the clinic where I had 2 POCT both negative (19 days & 39 days from possible exposure) I was told to come back and have another Duo. Duo result weak reactive, Negative(25 days & 46 days from possible exposure) I again had 2 POCT both negative. I was told that the reaction in the DUO tests could have been caused by a recent infection or flue which looks like the p24 antigens/antibodies but after further testing in the lab it was found negative.
After these results I have been in a state of anxiety combined with possible symptoms swollen lymph nodes in left side of my neck stiff neck, night sweats, tingling in toes feet and hands, headache which has been constant for week’s, tightness in chest, chest feeling bruised possible chest infection and generally feeling unwell. Not sure if this could be all down to anxiety/stress.
I decided to have a further tests DUO & POCT both NEGATIVE (42 days & 64 days from possible exposure) BUT symptoms still persist. I have been to the Doctors and have been tested for all manner of things with no conclusion. I am really worried that I have HIV.
I have been told/read that many experts have not seen a Negative HIV Duo test change from 6 weeks to positive at 12 weeks. Is this the case? I’m worried that the two initial Duo tests picked up the antigen (4th Generation EIA (DUO) test looks for both antibodies and p24 antigens. The p24 antigens are detectable immediately and only for 14-28 days post exposure) but the antibodies hadn’t been produced yet giving this reactive negative, weak reactive negative result. I had my final duo result at 6.3 and 9.1 weeks from the possible exposures which came back negative BUT I am not sure if I can trust this based on what has happened so far.
http://emedicine.medscape.com/article/1982802-overview#aw2aab6b5
The above article says:
"Current evidence has shown a second diagnostic window when using fourth-generation assays. In a case of acute infection, 2 fourth-generation assays were compared with 2 third-generation assays and 1 HIV antigen assay. Reactive results from the fourth-generation assays became negative during a second diagnostic window when HIV-specific antibodies were absent and p24 antigen concentrations declined below the test limits.[16] Similar finding have been reported in other case reports.[17]"
Could this be the case with me could my result at 6.3 and 9.1 weeks from the possible exposure be in the window period where the antigen levels have dropped but the antibodies have not been produced in high enough levels to be detected?
I’m so scared and stressed at the moment and are dreading testing shortly at 12 weeks. Please can you let me know your thoughts and how to comment on your response if necessary?

Answer: 

Hi there and thank you for using AIDS Vancouver Helpline as your source for HIV/AIDS related information.

It is certainly necessary for all sexually active individuals who recently engage in unprotected vaginal/anal sex to get tested for both HIV and STIs. HIV testing, however, is not necessary for those who engage in oral sex (either protected or unprotected) and protected vaginal/anal sex. Condom is invented for preventing unwanted pregnancy as well as HIV transmission.

Perhaps it is your anxiety making you judge your test results. A 4th Generation EIA (DUO) looks for both p24 antigen and HIV antibodies.

p24 antigen is a viral protein of HIV and is detectable earlier than HIV antibody during acute infection. It occurs early after infection due to the initial burst of virus replication. When HIV antibodies become detectable, p24 antigen is no longer demonstrable.

There are two main variations on the DUO test methods:
1. You can determine how much antibody is in your blood; or
2. You can determine how much protein (p24 antigen) is bound by an antibody.

An initial positive test result is required to confirmed by a Western Blot test for reassurance. Western Blot is required to follow up the initial positive test result in order to prevent false positive. Although false test results are rare, most of them are likely to be false positive than false negative.

Your test results at 42 days and 64 days are an excellent indicator of your negative status. Point of Care (POC) test detects can detect up to 95% of the infections within 28-42 days and is conclusive at 86 days, whereas the DUO test is considered conclusive at 42 days by many HIV specialists.

It is not a wise decision to conclude your status based on the "symptoms" you are experiencing. In fact, there is not yet a set of "clinically defined HIV symptoms" for doctors to replace HIV tests. That is because "symptoms" vary a lot and may not even appear in all people. For those who show symptoms, they would usually experience a strong flu-like illness 2-6 weeks after exposure. It is good to note that flu-like illness is a common reaction from our immune system to react to all kinds of infections that have nothing to do with HIV.

It is absolutely your personal decision to have a final test at 12 weeks, due to your high risk exposure (unprotected vaginal sex). However, the previous test results are already an excellent indicator of your negative status. Your negative test results indicates that you do not have HIV. Continue testing would not change the fact that you do not have HIV.

It is not our role to force you to stop testing. Our role here is to provide unbiased scientific information to audience. Therefore, you are really the only one to decide whether or not to take the test results and move on.

One single exposure may leads to high anxiety and worries, but it does not absolutely transmit you HIV.
If you wish to have further assistance, you can write a new question to us (make sure copy and paste this posting into your new question).

All the best,
Tina
AIDS Vancouver Helpline Volunteer