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HIV P24 Ag/Ab Test, Duo Test, Combo Test at our Clinic

Updated information on Rapid Anonymous HIV Combo test at our Clinics. 


Info leaflet for SD Bioline Combo Test

Info leaflet for SD Bioline Combo Test

I have been getting a lot of question with regards to the Duo test or Combo test as it is also known as.

Let’s first get some basics right:

Duo Test = Combo Test = P24 Ag/Ab test

All these terms refer to the same thing. Basically it is a test that simultaneously tests for the HIV P24 Antigen and the HIV antibody.

HIV Prevention within 72 hours of exposure (PEP) – Click Here

The HIV P24 antigen is a small piece of protein that is found on the capsule of the HIV virus. When a person is infected with HIV, these bits of protein can be found floating in the blood. The HIV P24 test is a test that detects these bits of protein. This test was first developed as a HIV screening test but rapidly ran out of favor due to the development of more advanced NAAT tests. (For more details on NAAT testing please read: http://www.drtanandpartners.com/nucleic-acid-amplification-testing-naat/)The window period for P24 testing is also very small. This test alone is only accurate for between 3 and 6 weeks post exposure. So it is a test with very limited applications unless combined with the HIV antibody test. The presence of P24 Antigens in the blood indicates a recent HIV infection.

Click here for details on getting the Combo test at our Clinics

We all already know that the HIV antibody test becomes quite reliable at 4 weeks and as good as conclusive at 6 weeks. Although most health authorities still recommend a 3 months window period. So putting these 2 tests together gives you a very powerful tool to diagnose HIV infection in as little as 3 weeks. Personally I prefer to conduct the Combo test at 4 weeks because I believe that is when the level of P24 antigen peaks in the blood giving us maximum accuracy.

In our clinic, we use the SD Bioline Rapid HIV Combo Test 2.0. It is a rapid test that takes only 20 minutes for us to get results. We are also approved to conduct this test as part of the Anonymous HIV testing Program.

The test is conducted very much like the HIV antibody test. All we need is blood from a finger prick. (For more details on Anonymous HIV Testing at our clinic please read: http://www.drtanandpartners.com/anonymous-hiv-testing-at-our-clinic/)

SD Bioline HIV Combo Test showing a positive result (2 red bars)

SD Bioline HIV Combo Test showing a positive result (2 red bars)










SD Bioline Combo HIV test showing a positive result. Note the test line is very faint. This could be due to a very recent HIV infection or the test could be false positive (1% chance).

SD Bioline Combo HIV test showing a positive result. Note the test line is very faint. This could be due to a very recent HIV infection or the test could be false positive (1% chance).










Multicentre clinical trials have shown 100% sensitivity and more than 99% specificity.

This kit has been registered with Singapore’s Health Science Authority (HSA).

So the Combo Test has many advantages including:

1. Earlier detection of HIV infection.

2. Rapid (20 minutes)

3. Anonymous

The only problem is that it costs more. At our clinic is costs $200 ($214 with GST).

Click on the picture for the latest information on the HIV testing Window Period

Click on the picture for the latest information on the HIV testing Window Period










Click here for HIV Testing FAQ

More on HIV symptoms.

If you have any questions, visit our free online forum on sexual health, HIV and STDs.

Click here for Info on STD Symptoms in Men
Click here for Info on STD Symptoms in Women
Click here to see the full range of our HIV/STD Services

If you need a HIV test visit Our Clinics anytime during our opening hours. You do not need an appointment.

We are now open on weekends.

Find out more about Anonymous HIV testing at our clinics.

Can’t wait for 3 months to find out? Find out more about Anonymous Rapid HIV Combo test at our clinics.

If you had a high risk exposure to HIV within the past 72 hours, you can take medicines to reduce your risk of actually contracting HIV. Find out more on HIV PEP Treatment.

We have 3 locations conveniently located at Robertson Walk and Bencoolen Street and Novena Medical Center.

We are Open on Saturdays and Sundays.

Click Here for Contact Details, Address and Opening Times.

Related Topics:

Anonymous HIV testing at our Clinics

HIV – Understanding the Window Period

Cost of HIV/STD tests at our Clinics

Condom Broke

Getting HIV from Oral Sex

More on HIV symptoms

How long can HIV live outside the body?

About Dr. Tan
Dr. Tan graduated from the National University of Singapore in 2001. His residency was in the two largest public hospitals in Singapore; Tan Tock Seng Hospital and Singapore General Hospital.

Find the profiles of our panel of doctors.


  1. hey doctor, im a 21 student. and i did the biggest mistake in my life at 6days ago. i had protected vaginal sex with a thai massage parlour in pattaya. it lasted about 1min~2min. Assuming the condom did broke, how much percentage could i get HIV? i am so scared right now :( do i need a test? 28days, 3months or 6months? i have no appetite and feeling nausea this few days, is it the symptoms? or is it because im too anxiety and depression? im really very scared now :( please help

    • About 1 in 100,000. Yes you do need to test for HIV and especially for other STDs. You can get the Combo test at 28 days.

  2. sanam singh

    Dr., what is difference between index value of 0.2 and 0.8 in p24 duo test. After 2 weeks of exposure my test value came 0.2 and after 6 weeks it cames 0.8. It increases. Does it increases more with time and at last become positive?

    • If it increases pass the threshold then it is positive. Having an increasing value does not mean it will definitely turn positive.

  3. Camilo Rpo

    Hi Dr Tan
    I’ve seen a lot of information on the internet that says you have to do test at 6 months, this situation occurs? I do a combo test at 28 days, I can be at peace with my negative result without waiting 6 months?

  4. sanam singh

    Doctor, is p24 duo test is conclusive after 6 weeks? Second- how many patients u saw which were negative after 6 week but found positive after 3 months?

  5. Concerned

    Dr. Tan,

    Is the Combo test affected by PEP? I took the combo test at day 49 post exposure to an unknown source (20 days after I completed PEP). It was negative. 1. Is this reliable? 2. Have you ever seen someone turn positive after these types of results?

    Thank you!

  6. sanam singh

    Dear doc., plz tell how many cases of hiv infection were reported due to insertive fetallio or penetrative oral sex?how many cases have u seen? Is got a blowjob from a sex worker without condom for about 20 seconds. Is this risky?

  7. Hi Dr Tan,
    I was using zaricort and saerogenta-a for treating my penile trush. Im still sexually active during this period but all are protected sex using condom. Informations frm internet saying that miconazole and clotrimazole can damage condom. Is that true? I did wash away the cream before i use a condom. Will this put me on risk of STI? Thank you in advance.

    • Even if you were not using the creams you are still at risk. Condoms are nowhere near 100% effective in preventing STDs. In fact, for things like Herpes, condoms are only 30% effective.

  8. sanam singh

    Hii doctor, i have done an insertive oral sex with a sex worker. After 12 days of exposure i done pcr rna test and p24 combo test. After 21 days again done p24 combo. Both came negative. Is this conclusive?

    • In my opinion they are conclusive.

      • sanam singh

        Dear doctor, plz tell how many chances will present getting infected by insertive fettlio(insertive oral sex).How many patients u saw infected by this type of sex?

  9. Sebastian r

    Dear Dr Tan, I was talking with two doctors and one told me it was just to check (repeat the test at 6 months) if you have risk and the other told me that at 3 months was already conclusive, as he had counting in the previous post made me two combo tests abbot architect of one to 28 days and again at 45 days and I do a third generation at 3 months. Then are these conclusive evidence Dr?

    • Dude, seriously, I am not going to comment on other Doctor’s recommendations. I will say in my opinion the Combo test at 28 days is conclusive. That is all.

  10. Sebastian r

    Dear Dr Tan, I am sebastian Restrepo of Colombia would like to ask, as I have done several tests but I have not found a doctor to tell me that these results are definitive. I’ve done a elisa fourth generation architect combo abbot at 28 and 45 days, since there was a lot of information from the conclusiveness of this test me make a third generation single antibody at 3 months, I want ayuduras me sleep well. Because there are doctors that speak of six months?

    • Different countries have different recommendations and guidelines. So although I believe that the Combo test is conclusive at 28 days, if your doctors are telling you to retest at 6 months, you must follow their advice. They certainly have their reasons.

      • Sebastian r

        But if the reactants are equal, there are reasons rather I stay their conclusions , they are outdated . Shall we say so ?

        • Wow. You are touching on a really raw nerve there. I am most certainly NOT going to say that Doctors in Columbia are outdated. I have the greatest respect for my colleagues wherever in the world they practice. I can only say that from the current scientific evidence that we have, the HIV P24 antigen and IgM antibody will invariably be detectable in patients infected with HIV by the 28th day after exposure. Therefore in my view the Combo test at day 28 is conclusive. Your Doctors have their reasons to recommend a retest at 6 months. I respect their opinion and you should too.

          • Sebastian r

            but the recommendations would go more for the next retest if I have other risk situation but that the reagents are different or something different compared to the diagnosis?

  11. Doctor Tan,
    I did a STD panel test from a reputed lab in india after 14 months of exposure. Among many test HIV was one of them. All of the results were negative. However I have one doubt regarding the HIV test and the generation of test conducted….In the report they have given as below for HIV test
    HIV 1/2 & P24 COMBO TEST
    INDEX VALUE 0.18
    I tried to reach the customer care service of the lab. However the customer care personnel didn’t able to provide me a clear answer. So I was bit tensed regarding the test that it might detect only P24 antigen and not antibodies.
    My questions are
    1. Did I took correct test?
    2.Does the test mentioned in report detect both antigen and
    3. To which generation the given test belongs ?
    4. Do I need to take additional test?
    5. Are p24 antigen only test are used nowadays?
    Dr Tan you are doing a great work here and thank you in advance….

    • What you should do is to take these results to a doctor and get a proper medical consultation. 1. I cannot answer this. 2. Yes. 3. 4th. 4. I cannot answer this. 5. Yes they are.

      • Thank you doctor.

      • Doctor Tan ,as you suggested I ll definitely take the reports to a doctor…
        But please let me know as I have taken HIV 1/2 & P24 COMBO TEST (CMIA) test after 14 months of possible exposure and result came as NON REACTIVE it should be 100 % conclusive right??

  12. Ali Khan

    Help me dr please

  13. Ali Khan

    Doctor, i went and get tested for HIV using the ALERE DETERMINE COMBO AG/AB test at 32 days and 42 days after giving blowjob to another guy for a short period WITHOUT ejaculation and the tests came out NEGATIVE. should i re-test ?

    • In my opinion your test is conclusive.

      • Ali Khan

        Thank you Doc, but is there a period where Antigen is too low and Antibody also too low for the test to detect after 4 weeks? I’m afraid that my 42nd day test did not detect both antigen and antibody. Have u seen anyone like this?

  14. hello doctor i risk hiv and I test combo p24 in 23 days so negative conclusion at this point is not?

    • It is as good as conclusive but not officially so.

    • Mr Phong

      Hi,I am from vietnam,and I did check up HIV combo two times.from 23 days and 50 days from the day I infected from HIV but resolve not HIV.can doctor be trust this resolve.

  15. Dr tan,

    I had a heterosexual with a girl which I met first time and got some trouble. When i put my finger into her vagina and that is bloodless, but I insert my penis into it and I found that is bleeding. I corcumcised since 5 years old. Despite my penis was not stay long in her vagina (2-3 minutes since I start insert) but I still worry to get the HIV.

    After that she has go to private hospital for hiv screening and get non reaction result. But I know that is a window period between 3 weeks to 3 months and that is possible to get infect. I am so worry to get it. Today is 4th day. Already past 72 hours.

    • Well, you had unprotected sex. That definitely puts you at risk of HIV. You are right to say she could be in the HIV testing window period. Which means her negative test may not be truly negative. Anyway, there is really nothing much you can do about it now. You have to wait till the window period is over then get tested. You should also screen for other STDs.

  16. Paranoid
    NOVEMBER 23, 2014
    Your comment is awaiting moderation.
    Hi doc I had a high risk of exposure a Month ago first test was HIV RNA test Nonreactive (2weeks) and I got Tested 31days after my exposure Using the test HIV ag/ab Combo test and my result came back Negative/Non-Reactive. The doctor check my mouth glands and she said good she ask me if I ever had a flu this past weeks I said no, not yet . And I ask my doctor if my test is accurate she said yes , but you need to comeback again after 3 months and that’s a long wait I’m so paranoid and stress now. I really appreciate your Reply Doc. Thank you Godblesd

    1. Does the Hiv ag/ab Combo is conclusive in that time frame ? Coz I read on CDC that that test can pick it up HIV infection in 3weeks after exposure.

    2. Is this test is the 4th Generation?

  17. lucozade12

    I had a strange “exposure” I was tricked into drinking a pint of a mixture of larger urine and vomit. I drank around half of it before realising and then went and threw up. I have had a negative duo test at exactly 28 days. I now have developed at 6 and half weeks a small rash of circular pink skin. It is not very visible and I have to look quite hard to see it. In your professional opinion was I ever at risk? Is my test conclusive.

    Thank you for taking the time to answer my question

  18. Hi Dr.Tan,

    Regardless of my theoretical risk(skin contact)of catching HIV,I had Hiv Pcr test (LOD:100IU/ml) at 2 weeks and 4 weeks after exposure and they all came back negative. I also got a HIV Combo test (4th gen)at 4 weeks and thankfully it was negative. Are my tests conclusive and definitive? And may I know if the HPV vaccine (Gardasil) taken 4 weeks before having had those tests would affect the results? It’s much appreciated for your kindness to set up this platform for us. Thanks a lot.

    • Oh yes they certainly are. That is seriously overkill testing. The Gardasil vaccine has no effect on HIV test accuracy. I appreciate the fact that you appreciate this site. Thank you.

      • Wow, that’s very kind of you Dr Tan. I never expected that I could have your reply as soon as you did (I won’t take it for granted), you are amazing!

        I’m so grateful that your answer upon my test results would reassure me much.

        Hopefully I could ask you for one more question about Combo test: I know that there is a rare group of infected people who can suppress their virus to undetectable level (some of them even make it less than 50copies/mL) and it might be the reason why PCR is not 100% (99.7% or more) conclusive after its “windo period”.
        I am concerned if the Combo test would be able to detect P24 antigen for the elite controller since P24 protein is part of the virus of HIV at 28 days or more after exposure given that antibody may not be produced enough to be detected and they can suppress the virus.

        With your reassurance, I’m literally confident with my negative “Overkill” tests at 28 days. Keep it up to introduce the latest information and technology in detecting HIV and other Stds to us, we badly need the doctors like you nowadays, million thanks!

        • Thank you for not taking us for granted. That is much appreciated. If you were indeed an Elite Controller or Long Term Non-Progressor, the Combo test will certainly pick up the antibodies.

  19. I had an unprotected oral sex on last year’s October and unprotected oral sex this year’s February both of my partner is a worker at massage shop. I did the test Ag/ab and the result is negative on 11th August 2014. so am i free from HIV?

    • In my opinion your test is conclusive.

      • thanks doc, i can sleep well now

        • That is a great reply. I am very happy you are feeling better.

          • so the screening test still accurate even its last year exposure?

          • Yes. Even if it was an exposure 10 years ago.

        • Dear Doc, I am from India, a FSW licked my penis head by her tongue for 10 second, no oral just licking by tongue, should I worry, I get tested combo test on 22nd day, do i need any further testing? … Regards

          • I think the risk of getting HIV from oral sex is very low in fact as good as zero. Click here for more info.

  20. Dear doc,

    I got protected sex with legal sex worker last month. I’ve tested HIV P24 Ag/Ab Test, Duo Test, Combo for 2 times, 21 days and 28 days and both are negative.

    Should i retest on the third month?

    In singapore is there any case like false-negative on the 28 days?

  21. hello doctor tan
    my question is also same but i am giving u full description of duo test
    check the link http://www.regentstreetclinic.co/hiv-aidsMEDIA/PosterHIVAIDS.jpg
    The duo test is exactly similar to this but not the same.
    there is written on that.
    and my blood line came on c that means negative am i rite.
    now my concern is all hiv duo test is conclusive plz relpy

    • Dude, honestly man. I really do not understand what you mean by “The duo test is exactly similar to this but not the same”. How can it be exactly similar but not the same? So is it the same or not?

  22. Hi Dr, i had sexual without condom at 14th Sep. The partner is working at massage centre. After 1 week+27days+31days i get a antigen and antibody combo test for HIV1/2 done, all the resulf show is non-reactive. i very worry about that..pls help me Dr.

    • In my opinion your tests are conclusive.

      • i make a test at 38 days again..the result show me oso is non-reactive..izit i still nid to test after 90days??

        • If the test you did was a combo test then you do not. If the test you did was an antibody test they you need to retest at 3 months.

  23. confused

    hi doc
    i had foreplay with sex worker smoching and suckinh breast i had cut in my mouth
    i tested after 22day duo test hiv1/2 came negative
    doctor said u dont need any futher test
    it is conclusive

  24. Dear Dr. Tan
    how accurate and conclusive is combo test at 34 weeks = 239 days post exposure?

    Thank you

  25. Hi doc

  26. Hi drs. Today mark day 27 of my exposure. Is it conclusive if I take the combo test today? Pls do reply me. Thank you very much.

    • Yes it will be conclusive. However, you might as well wait one more day to make it official.

  27. Dear doctors,

    Abbott AxSYM combo test at 40 days post exposure of receiving unprotected oral sex and frottage ( rubbing of genital with condom )

    Indicative or conclusive?

  28. Dear Dr Tan
    Regards to you.
    Please Help me.
    I am freaking out.
    I Had sex with a high class escort. During the intercourse the condom broke in between I noticed it and replaced it within 1-2 seconds. The girl confirmed to me that she was healthy. Got tested for HIV 1/2 & P-24(CMIA) combo test after 32 days of exposure which came negative. Had a rapid test at 58 days which also came negative. Again had a HIV 1/2 & P-24(CMIA) combo test after 66 days which also came negative. Do I need to go for further testing. Was worried as I found myself weighing 2-3 kg lesser which I know could be because of tense days I had. Kindly help. Shall be greatful to you.

    • Hi Neil,

      You needn’t worry. Your tests at 32 and 66 days show conclusively you do not have HIV. You don’t need any more further tests in my opinion.

      • Thanks for the cheering reply dear dr.
        Just wanted to ask ad to What could be the reasons for weight loss.
        I know I am troubling you, but if you could tell me about it.

        Regards & Thanks in anticipation.

        • It could be just normal variation or weight loss due to stress/ anxiety. See a doctor if the weight loss continues to persist.

          • Got blood sugar tests done today.
            Reports day 68-80.
            I hope that’s normal.

  29. Hi Dr Tan,

    I took this test (as described below) from Gribbles 48 days after possible exposure and both p24 antigen and hiv 1/2 antibody shows negative. The doctor adviced to retest every 3 months for 1 year. How accurate is it at 48 days? My other exposures are 3 months, 4 months and 6 months respectively (Total only 4 possible exposures in my life).

    HIV Ag/Ab Screening Assay
    The HIV screening assay performed by Gribbles Pathology is known as a “combo” assay. It detects not only antibodies to HIV which are generally produced 3 to 4 weeks after exposure, but also p24 antigen which can be present in detectable amounts at 2 weeks post exposure. This combination enables detection of an infected individual at the earliest possible moment by minimising the “window period” between infection and detection.

  30. Hi Dr.
    I had a possible exposure at least 7 years ago and I just got the antigen and antibody for HIV1/2 done and the tests came back negative. I read that the antigen levels drop after 4 weeks so is this test conclusive in my case? If not what other tests can I take?

  31. worried

    Sorry I forgot to add. I was not give pep because the girl tested negative.am not native english speaker sorry That is my persol best

  32. worried

    Hi doc

    Doc, I had sexual exposure on 29th july 2014. I used condom that broke. My partner was sex worker. After the accident I persuaded the girl to take a test. After paying her extra money she agreed. We had antibody test and all came negative.after 13 days I developed joint pains and got scared. After testing I become negative. That night I did not sleep. Then came bad sore throat that after taking antibioticts and anti inflamatory didnt disappear. Doctor changed my medication after eight days to azthromycin and anti allergy. I have red patch in my mouth. I have fever that is mild not burning fever. I have red patche on my inner thigh with whitish scales, spreading to my leg. I have fine rash on th face. I have burning kidney whch after doing urine result are negative.
    Yesterday I did alere determine combo test. Result negative
    Unigold antibody test. Result negative.
    Please doctor am really scared to death. Normally am healthy person who does not get this scary signs and symptom.

  33. Hi Dr.

    I would appreciate if you could give me some insights on my situation. Had a baseline test 9 days after possible exposure – negative. 3 weeks after exposure started having minor cold symptoms (fever 37.1 C, weight loss more than 5 lbs and sore throat) Went for another test in 22th day after the exposure (while having symptoms) again negative. I asked about the test they use, doc said that it is 4th generation. I read that this test is accurate as early as early as 3-4 weeks. But doc said that it is only 50% accurate at 3 weeks. I will go for another test at 6 weeks mark and 3 month for sure. But she also claims that at 6 weeks it is 75% accurate only.
    I would really appreciate your thoughts on the test accuracy to have a piece of mind. Also is it possible that the test might be 4th generation but not combo ( only antibody)

    Thank you in advance


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