Dr. Tan and Partners is one of the few approved Anonymous HIV Testing Centres in Singapore. A detailed write up on our service is available here.

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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

At our clinic the Combo Test costs $150.

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 4 locations conveniently located at Robertson Walk, Bencoolen Street, Novena and Scotts (Pacific Plaza).

Robertson Walk            6238 7810

Bencoolen Street          6884 4119

Novena                           63972095

Scotts                              66942348 (Opening April 2015)


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.

Consultation $20.00-80.00
Rapid test only $20.00
(not inclusive of test)
8am – 5pm $60.00
5pm – 9pm $80.00
STD screening
Standard HIV, Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and II $ 200.00
Urine – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas, NSU, Mycoplasma, Ureaplasma, Urine Culture, Candida $ 280.00
Urethritis and Vaginitis
Vaginal Swab – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas PCR, Gardnerella PCR, Candida PCR, Group B StrepNSU, Mycoplasma, Ureaplasma, Direct Microscopy, Candida, Vaginal swab culture $ 345.00
Comprehensive (Male) Blood – Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and IIUrine – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas, NSU, Mycoplasma, Ureaplasma, Urine Culture, Candida $ 390.00
Comprehensive (Female) Blood – Syphilis, Hepatitis B/C, Herpes Simplex Virus Type I and IIVaginal Swab – Chlamydia and Gonorrhoea PCR, Monilia, Trichomonas PCR, Gardnerella PCR, Candida PCR, Group B StrepNSU, Mycoplasma, Ureaplasma, Direct Microscopy, Candida, Vaginal swab culture $ 525.00
Individual STD Tests
Determine Syphilis test Rapid Syphilis Test $ 50.00
Determine Hepatitis B Test Rapid Hepatitis B Test $ 50.00
Herpes Simplex Virus PCR Herpes Simplex Virus Polymerase Chain Reaction (PCR) Test $ 190.00
Chlamydia and Gonoccocal PCR Chlamydia and Gonorrhea  $188.00
Herpes Simplex Virus Type I IgG Antibody Herpes Type 1 $ 40.00
Herpes Simplex Virus Type II IgG Antibody Herpes Type 2 $ 40.00
Non-Specific Urethritis (NSU) Culture Mycoplasma, Ureaplasma $ 118.00
HIV test
HIV RNA/DNA Polymerase Chain Reaction (PCR) Test $600
Add $100 for expedited results
Rapid Fingerprick Blood HIV-1/2 P24 Antigen/Antibody Combo (HIV Duo Test) (4th generation!) $ 150.00
Rapid Oral Saliva HIV-1/2 Antibody Test (Oraquick) $ 50.00
Rapid Fingerprick Blood HIV-1/2 Antibody Test (Determine) $ 50.00
PEP $2000 – $2200


  1. Hello

    Is an rna pcr at 19 days combined with an antigen test at 26 days conclusive?

  2. Dear Doctor Tran,

    I would like to ask you the following,

    I had unprotected sex with 2 females and 9 days later i had symtoms as sore eyes, mouth uclers, headache, chills and sore throat.

    Since then i had 2 rna pcr tests at the 11 day of exposure and at 19nth day also at 26 days and 10 hours after the exposure i had the hiv duo 4th generation test and all of them were negative.

    Do you think that there would be a chane that i am infected?( i have read that if the symptomsnare due to hiv tests will pick it up)

    Does the hiv duo test would be hoghly reliable at that point of time??

    Thank you for your time!!!!

  3. Hi Doctor i had visitied you clinic and got 4th generation P24 test antigen antibody on 25th day of exposure.Is it conclusive.

    Also later after a week if i touch much neck feel my lymp node is swollen a bit.

    Please advice

    • Dr Justin Sim

      Technically the test is conclusive at 28 days or more but the doing it on the 25th day is so close to 28 that it is enough to be conclusive. Your neck swelling is being caused by something else.

      • Doctor do you suggest me to do another test I am at 35 day mark.

        • Dr Justin Sim

          Personally, it is not necessary but you can do so for peace of mind.

          • Hi doctor today I had been to your clinic and did a combo test again unfortunately coudnt meet you as was told you are on personal work but the other doctor examined me well . my 38 the day p24 test came negative.

            My only worry is I still have small right side neck cervical node swollen a bit below the jaw .

            I have done 3 combo test at your clinic 15th day 25th day and 38th day all were negative.

            Still worried if it will change after 3 months due to this swollen right neck node swelling.

            Please let me know if u ever had a patient who got negative results like mine and changed later.

  4. Alexandra

    Hi Doctor,

    I had both an RNA QL test and a 4th generation test done at 24 days post exposure. Are these results conclusive or do I need to go on for another 4th gen after 28 days? Thanks!

    • For all intents and purposes they are conclusive. However, they may not meet your local HIV testing guidelines. I suggest you see your local doctor for confirmation.

  5. Hello dr tan , i’m hisyam from kuala lumpur actually my last exposure on 6/7/2015 . and my first checked 21/7/2015 at pathlab . my results hiv 1&2 ag/ab elisa non reactive . siplis thpa vdrl non reactive , herpes 1 reactive . herpes 2 non reactive . chlymdia non reactive . then i do my second test at pathlab also a few days ago 17/8/2015 and my results comeback 18/8/2015 . hiv 1&2 ag/ab elisa non reactive . huh ! im so scared . i want to ask u should i do repeat test or not ?

    • Dr Justin Sim

      Your results are reassuring but you need to repeat them as they are being done a little too early. The HIV test needs to be done 3 months from exposure. Same for syphilis and herpes.

      • but is not conclusive on 28 day ?

        • but dr tan tell me its 4TH GENERATION AND ITS CONCLUSIVE which one ?

          • Dr Justin Sim

            Apologies I didn’t see the second date you put in because of spacing. But the second test is 4th gen so it is conclusive.

          • haha , its ok doc , thanks for advise , & information send my regards to dr tan

    • Hello doctor.
      I had an Elisa Test (Chemi/Luminescence) and Hiv Duo Cmia test at 8 weeks after possible exposure. The results came negative for both. Can I consider these to be conclusive ?
      I read in a forum that Duo tests give best results at 4-6 after possible exposure. But since I did mine in 8 weeks, will this reduce the accuracy of the Duo test ?

      • Dr Justin Sim

        Do not worry it will still be conclusive. After 8 weeks we should be ablt to start detecting the antibodies even if the antigen is gone.

  6. Dear Dr,
    I would like to know that i have been gone protected sex with female but after i didn,t wash my privet part and after few days i start feel that i may be infected .I went to Dr who precribed me to go for test like HIV,VDRL.both the result was negative.Infact HIV was tested with DUO 4th generation after 62 days of sex.But still i used to worry a lot.I feel to muchh tense and scare again to get tested.My question is after 62 day report is negative then is there any thingh to worry.I am having SOMITISATION DISORDER problem also as diagonised by phycetric.Please help me

    • Dr Justin Sim

      Your doctor is correct in that somatisation plays a part. Your HIV test is conclusive but you should get tested for other STDs like gonorrhoea and chlamydia.

  7. Dr Tan i had really high risk for hiv . Vaginal intercourse with a hiv positive man
    i took 3 tests – ac anti hiv duo eclia serum plasma tests .
    one at day 30 last exposure , one dat day 47 and one at day 62 last exposure . Are those tests fourth generation and how reliable are they at day 62 ? Would you call them conclusive ….
    Will they change and do i need more testings ? Thank you in advance if you answer me

    • It sounds like a 4th generation test. You may want to check with your doctor. If it is a 4th generation test, then it is conclusive and you do not have HIV.


    Hello doctor:
    Last month on 22nd July, I had sex with a Thai girl from one of these legal brothel. We used condoms, but I’m afraid that the condom peeled off. It has already past 21days yesterday and I went to your clinic at Robertson Walk and took the 4th Gen rapid combo test and I get a negative result. So, is this result reliable? Will there be any possibility that the test kit showed a false negative since I went through many forum telling about false result of thid SD test kit,and am I frer from HIV now? Do I need to check again? Thanks!

  9. Sean123

    Dear Dr…I’m Dying of anxiety!

    I sent a message a little while ago but guess it was not posted.

    Long story short..Had unprotected anal sex with two females who’s HIV status is unknown in 2012 and latest in March 2013.

    Now that I’m married and wife is 5.5 months pregnant.She was asked to do a HIV test and was done through a local clinic which the result indicated as “Weakly positive”,Twice!

    Upon instruction of her Gyno we both tested for HIV antibody 1 & 2 (ELISA) from ISO 15189 accredited lab and showed the results were “Negative”. Its been more than two years since my last exposure.Can i still be infected or can i treat the latest lab results are conclusive.

    Please Please Please help me!

    • Pregnancy is a common cause of false positive HIV tests. Your ELISA tests are both negative. I don’t see a reason for you to be concerned.

      • Sean123

        Dear Dr.Tan,

        I know you may have heard this 1000 times but your words means everything to me. More than that i appreciate your immediate response.I’m from a developing country and online help for this kind of a matter is literally non exist here.I believe your word and assume i can move forward with a peace of mind!

        The worry i had was the repeated weakly positive results from the local lab. Hope it’s not a concern since the latest reveal that both of us are Negative.

        God bless you and your loved one’s Sir! Please keep up the good work you do for many people like me.Because for some you will be the only help available!

        Thank you!

        • Sean123

          Dear Dr.

          Sorry for flooding the page with my concerns.

          Do you think my results are conclusive?

      • Sean123

        Dear Dr.

        Would you prefer that my result to be conclusive? Even though the latest results indicate that both of us are negative I’m worried about the previous result(TWICE) which gave a “Weakly positive” for my wife.

        Please be kind enough to answer only for this one Dr. I beg you!

  10. Sean123

    Dear Dr..PLEASE HELP ME!

    First and foremost i appreciate the great help you provide to the online community!

    I had unprotected anal sex two females who’s HIV status is unknown.One was in 2012 and the latest was in March 2013.

    Now that I’m married and my wife is pregnant for 5.5 months. She was tested for HIV from a local free clinic which the result came as “Weakly positive”,TWICE!

    I told this to her Gyno who is from a very reputed hospital and he asked my wife to do HIV 1 and 2 Antibody and the result came out as “Negative”.(Method ELISA).I also underwent the same test from the same lab after four days and mine was also “Negative”.

    Lab of the hospital is ISO15189 accredited and the results are widely accepted across the country.

    MY QUESTION IS: Can i accept the result of the lab as conclusive despite of the “Weakly positive” alerts given by the local clinic.It’s been more than two years since my possible exposure and this was the very first test i did to check the HIV status of myself.

    Please help me as my soul is burning assuming i have possibly transferred an incurable disease for my better half.Showed the results to Gyno and he said there’s nothing to worry since the reports are “Negative”.(I saw there can be “false positive” test results in the early stage of pregnancy).Please Please Please help me!!

  11. i had an ag/ab hiv combo at a laboratory, they took the sample from my vain and i had to wait 2 weeks to get my result back

    i got this test exactly at 6 weeks mark the possible exposure to hiv which was insertive oral sex (someone performe oral sex on me)

    i am really worry because i just got this negative test and i just want to know if i have to trust it or repeat the hiv test. thanks.

    • Dr Justin Sim

      If you had the antibody only test then you should repeat at 3 months. However, the risk of HIV from oral sex is negligible.

      • Dr, are you telling me that the 4th generation ag/ab hiv duo combo is not yet conclusive at six week, I took this test in a laboratory here in the state I am currently living it came back negative.

        Then I took another 4th generation ag/ab hiv test exactly at 77 days at a private clinic where the sample is send to a lab called quest diagnostic.
        Well, the test came back negative, should I retest again? Or is it conclusive?
        Note my risk was very small.

  12. Dear Dr. Tan

    Would the 4th gen test be conclusive at 24 days ?

    Thank you !

    • Dr Justin Sim

      Ideally you need 28 days to be conclusive but at 24 days it is unlikely to make too much of a difference. You may still want to be tested after 28 days to be sure.

  13. Should I Retest

    Hi Doc,

    I did a total of three tests after my sexual exposure (protected sex, unprotected oral sex) which was described as a relatively low risk. However, I did not want to take my chances.

    As such, I took the following tests:

    – Fourth generation test at Day 12
    – Third generation test at Day 39
    – Fourth generation test at Day 49

    Based on your professional opinion, if I were your patient, would you consider my results conclusive?

    I hope to hear from you soon.

    Thank you, Doc!

  14. Andy Chen

    Hello Doctor Tan,
    I am from China,and I had a possible exposure to HIV in February this year. After that I took two standard HIV antibody tests at 5 weeks and 11 weeks and two HIV 1&2 ab and p24 ag tests (using Roche HIV Combi pt) at 10 weeks and 14 weeks. However during this period, I have been diagnosed with HCV positive.
    Here is my question, Have my HIV tests conclusive given my apparent HCV infection? If not conclusive, what’s your suggestion for my next move?

    Thank you very much, hope to see your reply!

    Best regards,
    Andy Chen

    • Andy Chen

      I am sorry Doc Tan, I forgot to mention that all my four HIV test were negative.

    • Acute HCV infection can prolong the window period for HIV. It is recommended that your doctor follows you up for up to 1 year from your last high risk exposure. This means that you should get re-tested for HIV throughout the period of follow up. It is best to speak to your doctor when your next test should be.

      • Andy Chen

        thank you,doctor. One last question, you mean even my negative Duo test at 14 weeks won’t suggest a negative results? I understand acute HCV infection can prolong the production of antibody of HIV, but how about p24 antigen?

        hope to see your reply.

        • It should not really affect the antigen. But it is still recommended to be followed up for at least 1 year to make sure you are clear of HIV.

          • Andy Chen

            thank you, doc

          • Andy Chen

            Sorry about any inconvenience, doctor, but from your website,I noticed that there was a update towards the topic of “HIV and Hep C co-infection window period”, saying that “Update 10th December 2014-The latest published guidelines have not mentioned HCV prolonging the HIV testing window period. This could be due to that fact that most guidelines now recommend the 4th Generation combined Antibody/Antigen assay as 1st line screening for HIV infection.”

            Not questioning your considerate suggestion, just interested in checking some truth.

            Thank you, hope to see your reply.

          • If you have had a 4th generation HIV test done after 4 weeks from exposure and it is non-reactive, I can safely say that you do not have HIV. Perhaps you could also check with the doctor who did the test for you. In my opinion, you would still require an antibody check at 6 months and 12 months just to be on the safe side.

          • Andy Chen

            Thank you for your patience, doctor. I have asked my doctor and he said they were 4th generation tests (using Roche Elecsys HIV Combin reagent). And I will follow your considerate advice.

          • You are welcome.

      • Andy Chen

        for more information, my exposure was a sexual one..

  15. Hi Doctor

    I had sex 33 days ago with a woman. Condom slipped off during the sex.

    I did a test on day 32 it was negative.
    It’s a rapid card test.

    Test is called Alere Determine™ HIV-1/2 Ag/Ab Combo Rapid Test

    Can I trust this test? Do I need to retest later?

    Ppl on Internet are saying that I need to do a laboratory test.



    • Dr Elaine Loh

      The HIV combo test is conclusive 4 weeks post exposure. If you want to be completely certain, no harm rechecking at 3rd month post exposure to be absolutely sure with antibody test, can be done either via rapid test or lab test.

      • Worriedguy

        Hi Elaine
        Does it mean 4 weeks duo test is not completely accurate ?

  16. Arturo Diaz

    Hi again, Dr,

    Pls, i need your advice. Here is my test results:

    1st. Test: ECLIA 4th gen (Lab) Ac/Ag p24). 42 days after exposure with a man (he was attempt penetrated me for 10 mins, without condom, but finally he didn´t because i feel pain and fear) and 28 days after performed a unprotected cunnilingus to prostitute. NO REACTIVE

    2nd TEST: Rapid test (inmunochromatography 3rd gen) 69 days after exposure with the man and 55 days after risk with the prostitute. NON REACTIVE

    3rd TEST: ELISA 4th gen (Lab, chemioluminiscent Ac/Ag p24) 69 days after with the man and 55 days after risk with the prostitute. NO REACTIVE

    4th TEST: ECLIA 4th gen (Lab, Ac/Ag p24) 87 days after exposure with the man and 72 days after exposure with prostitute. NO REACTIVE

    Do you think those results are conclusive? or need retest further.

    Thank you so much.

    • Your 2nd test is inconclusive because 3rd generation test is only conclusive after 12 weeks. The others are conclusive.

      • Arturo Diaz

        Thank you Doctor! So, this mean i don’t need re-test anymore?

        • In my opinion, you do not need to. It is best if you ask the doctor who did the test for you.

          • Arturo Diaz

            Thanks again, my doctor say the same: No more test required. And another two doctors on line: Andy Velez (POZ forum) and Sonia Helman from Argentina.

            Also performed test anti VHC, VHB and Sifilis, 55 days after exposure. All negative

            It´s just i´m affraid because i don’t now if is possible a later seroconversion, but now I will try to stay in calm, and will retest over 6 months, just for peace of mind. God bless you.

          • Thank you. Relax and move on.

  17. Nathan

    Hello Doctor,

    I’m planning to get the HIV Ag/Ab Screening Assay from Gribbles here in Malaysia. On the Gribbles website, they mentioned that the HIV screening assay performed is known as a “combo” assay. I’m planning to get this test done at intervals of 31 days, 8 weeks, 12 weeks and 6 months post exposure.

    My question:
    1. Is the test conclusive at 31 days? (i.e if i’m tested negative on day-31, is there still a chance for me to be positive on the 3rd month?)
    2. Is there a need to repeat the test at 6 months or can I just stop the retest after 3 months?

    Appreciate your feedback. Thanks.

    • Nathan

      by the way this HIV 1 and 2 Ag/Ab screening assay is performed based on ECLIA principle. Thanks.

    • Dr Justin Sim

      Combo tests should be conclusive at 28 days or more from exposure but because I am not familiar with this brand you may need to research more into this to be certain. If you are worried then do one test at 1 month and a second test at 3 months to be sure. Usually it is not necessary to repeat at 6 months, 3 months is enough.

      • Nathan

        Hi Dr,

        Ok thanks for the info. Will do the test at 1 mth and 3 mth intervals. By the way, this is the info provided on the HIV Ag/Ab test:

        ‘The HIV screening assay performed 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.’

        Am hoping this is similar info to the 4th generation HIV test. Thanks.

  18. Hii had unprotested sex with CSW in simgapore and really worried now.

    Got PCR RNA done at 10thday which is negative
    Got CMIA test done at 22nd day which is also negative
    Got ELSIA test done at 23rd day which is also negative.

    • Your PCR RNA test at 10th day should be able to detect HIV if you have been infected. I would suggest you get a 4th generation combo test done after 28 days.

      • Thanks
        Do you mean the CMIA test might not be accurate at 23rd day
        What are the chances of it being false negative
        Please i am worried now.

  19. Amelia

    Hi Doctors,
    I’d like to ask some questions. I got myself tested twice… The first one is around 35 days after exposure and the second one is 50 days after exposure. The result stated Anti HIV HIV Ag/Ab Combo (CMIA) 0.17 for the first test and 0.27 for the second test. My questions are…why is the titer of the second test increased? Should I consider that. Is it still non reactive? Is the second test conclusive? Should I get myself tested again after 3 months or it’s just for the peace of mind? Thanks a lot for your reply.

  20. Cindy Ramirez

    Hi Dr. Tan,

    I took a CMIA 4th generation HIV test and tested negative. I took the test 112 days (16 weeks) post exposure. Is my result considered conclusive? or should i test again?

  21. Arturo Diaz

    Sorry if i asked too much, only one question more… Can the Hepatitis C change the window, even to the Combo Ac/Ag p24 4th Gen test? What do you recommend in case to be positive with Hepatitis C? Thank you!

    • Yes, acute hepatitis C can prolong the window period for HIV. If you are worried, go get tested for Hepatitis C. If it is negative, move on. If it is positive, you may want to repeat your HIV test in 3 months.

      • Arturo Diaz

        Thank you so much dr. I also performed today a HCV, HBV antibody test and give me the results in 2 weeks. Sorry but last question: Am i in the correct window period for HVC testing, 54 days from last exposure?

        • Yes you are. The results will be accurate.

          • Arturo Diaz

            Thank you doctor.

          • Arturo Diaz

            Hi again Dr, today i visited the most important institution in Mexico City (Clinica Condesa, where i was performed my last 4th gen test). I question them about HCV and the window period of VIH and they say there are no way to undetected p24 and “some” others components of the test… Their conclusion is i have not HIV. Even if they detected HCV in the future.

            They consider conclusive their testings in 45 days by Inmunoanalysis Chromatographic 4th Gen technique.

            I dont know what think. Their test and info is not accurate in mexico?

            I´m very confused. Is there any risk even when i performed 2 HIV 1-2 Ac/AG p24?? 1st 28 days after last posible exposure and 2nd 55 days after posible exposure?? What happened with p24 and all medical advances??

            Thank you so much and sorry by the insistence!

          • The bottom line is, the test you took is conclusive after 28 days. Acute HCV infection can potentially prolong HIV window period.
            Based on your description, you do not have HIV. Please stop worrying.

  22. Amelia

    Hi Doctors,
    I am married and only have sex with my husband after marriage. My husband and I have a long distance relationship. Let me begin on May 9, 2015 (which I’m afraid to be the first exposure) and until now we have regular sex. On May 21, 2015 (around 12days) I had sore throat and white patches on my tonsils. My ENT in Indonesia gave me Augmentin 500mg for 5 days and the patches were gone. I had myself tested for HIV test on June 15, 2015 (around 37 days) in Indonesia after the first sex intercourse that I suspect…I went to a supposed to be trusted and well known laboratory but I don’t know what kind of test that they use..The result stated that they checked Anti HIV HIV Ag/Ab Combo (CMIA) 0.17 which is non reactive I think, but I’m worry about the 3 months window period. My question is…is the result from that laboratory correct and conclusive? So I am HIV negative? How about the white patches that I had at around less than 2weeks after exposure? Why did I have that if my test result is non reactive?
    Your reply will really really help me. Thank you.

    • HIV Ag/Ab combo test should be conclusive after 28 days. You may want to clarify with the lab what test was done. Sore throat with white patches on your tonsils sound like a tonsil infection (tonsillitis). I do not think it is related to HIV. If your test was a HIV Ag/Ab combo test, then you do not have HIV.
      If you are worried, get yourself tested again in 3 months time.

      • Amelia

        I just clarified with the lab..they said they used HIV Ag/Ab Combo (CMIA) method. They said if the result positive then they will check with other 3 methods, but since mine was non reactive…they said only 1 time check. Is that accurate and conclusive? Sorry if I asked too much. Thanks for your time.

        • Yes it is conclusive. HIV Combo test is conclusive after 28 days. You do not have HIV. If you are really worried, you can repeat a test at 3 months for the peace of mind.

          • Amelia

            Thanks for your reply, Doc.

          • Amelia

            Hi Doc, I just got myself tested again…so it’s about 50 days after exposure and it is stated Anti HIV HIV Ag/Ab Combo ( CMIA) 0.27. Why is the titer between the first (0.17) and second (0.27) increased? What does the increased result mean? Is it really non reactive?

          • As long as it falls below the lower limit, it is non-reactive. Don’t worry about the number. You can safely ignore it.

          • Amelia

            Hi Doc, I just got myself tested again…so it’s about 50 days after exposure and it is stated Anti HIV HIV Ag/Ab Combo ( CMIA) 0.27. Why is the titer between the first (0.17) and second (0.27) increased? What does the increased result mean? Is it really non reactive?

          • please see my other reply

  23. Wong V

    Hi Dr.
    I have a HIV RNA test done on 11th day of risky encounter which came in negetive? Should i get any more tests at the end of window period?

    • Dr Justin Sim

      At 10 days or more then HIV RNA test is conclusive. You may want a repeat test later on for peace of mind but this is not necessary.

      • vincent W

        I got myself tested for ELICA today which is 22nd day after exposure
        The result is 0.4 negetive.
        Is this ok? Last week when i tested it was 0.16

        • The ECLIA test you did was either an antibody test or a combo test. Both of which cannot be conclusive at 22 days post exposure. You need to retest. Th rising index number is NOT a sign of infection.

  24. fengyi

    hi…dr tan…can i take syphilis tpha test at 9 weeks post exposure..can it be accurate? Or I have to take vdrl test?

    • Dr Justin Sim

      Either test can be done but we usually suggest getting the VDRL test done first as this is cheaper and more readily available. VDRL looks at your disease activity and will be positive in new as well as old treated cases of Syphilis. Should VDRL be positive then TPHA can be done to test for current active disease. At 9 weeks we will get a very indicator but technically the tests are conclusive at 12 weeks or more.

  25. hallo drs,is syphilis test negative at day 77 from last exposure conclusive?

    • Dr Justin Sim

      In all likelihood yes but remember that Syphilis tests may not be fully conclusive until 12 weeks (or 90 days).

  26. I have tested hiv western blot after 40 days exposure result: negative and Rna pcr quantitative test after 48 days exposure test deduction limit 72 ml/copies
    result : below deduction limit 72 ml/ copies
    Please advise me doctor cam i go futher test

    • At 48 days post exposure why did you do the WB and RNA PCR? You should just do the combo test.

  27. Hi Doc,

    Can I get tested 14 days after exposure? Will it be accurate?

    • If you are talking about combo test, no it won’t be accurate. However, HIV RNA PCR can detect HIV after 10 days from exposure.
      HIV combo test is only conclusive at 28 days

      • Thanks for the reply, but Afa stated in their website that their 4th generation test is accurate 14 days after exposure. Is this because you are using a different test?

        • You may want to ask Afa regarding this. As far as we are concerned, our 4th generation HIV combo test is conclusive after 28 days. The test can detect HIV antigen after 14 days (if antigen is present). However, it is not conclusive especially if the test is negative.

  28. Hi Doc,

    Am planning to go over to your clinic for a HIV rapid test.
    i am wondering if at 23 days after exposure, will the results reverted after the test be as conclusive / accurate as the results on 28 days exposure?

    Thank you in advance!

  29. Hi Dr Tan,

    I just visited you today for the combo test (great experience, nice to talk to). Out of curiousity, is the lancet used for the finger prick sterilized prior to every new visit, or is a new disposable one used for every patient.


    • Dr Justin Sim

      A new disposable lancet is used every time. They are built with a safety mechanism only allowing them to ‘fire’ once.

      • Alright, thanks!

        Another question, assuming I did the test at 32 days, are there any chances this timing falls into the category of the ‘second window period’ mentioned in this article?


        Is the information in this article credible?

        Thanks in advance!

        • Dr Justin Sim

          It will be difficult for me to comment on another article on a public forum such as this but I will say that if you did the 4th gen test at 32 days, it would be conclusive. Our reasoning is that in the majority of cases, even if the antigen is dropping, the antibody should be rising in tandem. This means the 4th gen test will still pick up one or the other. The chance of taking a test in the short window period when both antigen and antibody is not detectable is slim.

          If you wanted more information on that article it is best to speak to the clinic that posted it.

  30. Sadness

    Hi doc..I just having a test which is hiv1 & 2 antibody & antigen..is tis combo test..?

  31. Wonderer

    Hi doc, the price for the combo test is 150. Is it GST inclusive and is it also consultation inclusive? I would like to know the total price just for combo test (consultation etc) so I can prepare beforehand before I head over. Thanks a lot!

  32. Dr Tan, I have unprotected sex with a guy who uknow hiv status…I am worried so I go for a check at lab which using CMIA ag/ab screening test on 47 days after exposure it came back non-reactive ..can it be conclusive or I need to retest again on 3 month?

    • drtan

      In my opinion the Combo test that you took is conclusive anytime after 28 days.

  33. Hi Dr. Tan,
    I have unprotected sex with a CSW in Bangkok. After 3 weeks post exposure, I have done the HIV I/II Ag/Ab test in Malaysia Pathlab. The result is non-reactive.

    Thus on the 4th week, I had experienced urine pain but I did not do any further test. On the 6th week, a doctor has taken my blood sample to test for all STDs, including HIV I/II Ag/Ab test by Gribbles. The result for HIV is again non-reactive. However, the test also showed that I had Chlamydia. I had to take 2 courses of Zitromax.

    It is 9 weeks and now I have mild fever and diarrhea for the past 2 days.

    I wish to wait for 12 weeks to perform another HIV test but I am worried now if the 3rd week and 6th weeks test are conclusive? Is the Malaysia lab using the same test standard as Singapore?

    I can only be back to Singapore on the 12th week and do a test in your clinic.

    Please advise should I test in Malaysia again now?


    • Dr Justin Sim

      I cannot say for sure if Malaysia uses the same standard of tests. What you can do now is get the 4th generation rapid combo test done as this will be conclusive for your timeframe. If you wait until you can see us at 12 weeks we can still do the same test.

      • Thanks Dr. Sim,

        Is the 6th week test showed good indicative even though I was confirmed having Chlamydia?


        • Dr Justin Sim


          • Hi Dr,
            I could not wait till 12 weeks. I went to another lab test using HIV Ab/Ag CMIA. The result come back is NON-reactive.
            It is 10th week by now and is this result conclusive? I am still under Chlamydia treatment. Thanks


  34. dear Dr. I got tested at DBS /AFA/ by 4th generation test. The kit seems same one as your clinic uses. But when I saw the kit there were two res lines, i dont exactly remember, I think one was on C, the other one was in above the C. The dr or consultant said the result is negative and showed me the kit. But when I asked what is the one red line on the kit, she said this is for test complete sign. I just belive in her. but when I checked the internet its stated that there must be only one res line to show negative. Am I right? Can it be possible there are two redlines whcih stand for Complete and Control? Thank u Dr

    • I am not going to second guess the doctor you saw. If she says it was negative, then I do not see any reason to not believe her. As far as I know, a negative test has 1 red line at C which stands for control. If you have any further queries I suggest you bring it up to AFA.

  35. Hello Dr. Tan

    i tested on 4 weeks mark using HIB Combi PT test by ROCHE.

    is this conclusive?

    thanks alot for ur time.

  36. Hi Dr tan,
    I had a risky exposure (anal i was receptive) where I acquired gonorrhea. 30 days after exposure I had a 4th generation Elisa p24 antigen test that came out negative, this was in the USA. Also I had no typical HIV ads symptoms, just gonorrhea symptoms.
    Can I take this as conclusive and if I tested at your lab would you recommend further testing?

  37. Dear Dr. Tan,

    I have the following results:
    Alere Combo Day 10: Faint positive obtained.
    SD Bioline Combo Day 28: Negative obtained.
    SD Bioline Combo Day 35: Negative obtained.
    Alere Combo Day 62: Faint positive obtained.
    AHP Test Kit Day 62: Negative obtained.

    Why is the result always changing, as it is always faint positive for the Alere Combo Rapid Test Kit but all negative for the other test kit?

    Any advice on this? I am very confuse.

    • Dear Dr. Tan,

      I am worried, can you help me on this?

      • i recommend you take eclia combo if you are within six weeks to three months , ifree you are beyond three months you can take eclia , a combo test looks for antibody as well as antigen , the more reliable way is to take the antibody test after three months , i hope you were not on pep , that would finalize in six months , if you are below the cut off then you dont need to test further , if you are above then you may need a western blot , keep in mind that western blot can come up inconclusive in healthy individuals who are not infected , stop at whatever stage you are negative , if positive or indeterminate then rna pcr is the final test which tells whether the attack is under control or the it is going towards a disease , if god forbid a pcr is positive then the only solution is medication as advised by the doctor if you are willing to take it

  38. If a person is infected HIV2 it would stay within the range of the 28 days ? . Studies on this? The cdc only talks about igm for HIV but is not clear about the HIV2

    • Very limited studies on HIV 2. Personally if I suspect HIV 2, I would test up to 3 months.

      • Dr, but you elsewhere in this forum said igm the vh2 are collected not later than the 25th then what is telling me is contradictory.

  39. Hello doctor, does the hiv duo second window period exist, where the ag/ab are both below the threshold, thus providing false negatives? You said the test is conclusive at 28 days, does it have to be exactly 28 days or is more than 28 days also conclusive ( don’t mind if this sounds stupid).

    • I have actually answered this question a few times before. You are asking if there is a cross over point where both the antigens and antibodies are too low for detection. As far as I know, this does not happen. The combo test is conclusive at 28 days and anytime thereafter.

  40. Sebastian r

    Dear dr tan, The test detects combo igm maximum at 24 days as you and I’ll explain the question is this includes hiv 2?

    • Sebastian r

      Dr please is for my hope

      • ab ag combo targets hiv 1 ag at three weeks and both hiv 1 and 2 ab at six weeks , if the result is negative and the number is not too close to cut off then you dont have hiv , in case of pep you can only test at three months for sure

  41. Sebastian Rpo

    Dr., Thank you for the support. I tell him that I do a test architect combo abbot to the exact 28 days and gave me no, but I wanted you to get an queries about this and to end this episode of my life;

    1.Is this kind of combo conclusive test at 28 days?
    2.I call attention to a response of this page is:
    Have there been any occasions in which you or indeed fellow colleagues of yours have found a 28 day negative turn positive?
    R/: Yes – but only with people who were clinically ill at the time, had very high risk exposures (with others who had recently become infected and so their infectiousness was very high) and so they clinically generated a high degree of concern on our part. I should say though that there are tiny numbers of these – perhaps 3 in 5 years and with the numbers of tests we do per year this is miniscule. In someone such as yourself where even if you had had vaginal unprotected sex with a female of unknown status I would regard the result as certain

    3. The question dealing with this is that if there is possibility to change the result in people suffering from cancer or other issues? I’m healthy I would have no problem?

    4. For a test to be conclusive at day 28 no matter what level of risk you have taken, what matters is that the test is negative.?

    5. This is another of the paragraph that caught my attention

    From the Freedomhealth point of view, using as described above the combined knowledge and experience of the team we regard the HIV DUO test as a conclusive HIV test at 28 days or beyond in almost all circumstances. In situations where a patient has had an exceptionally high level of HIV exposure and has symptoms which we might in our expert opinion regard as suggestive of an acute HIV infection, we will encourage the patient to re-test at an appropriate interval which we will decide with the patient. However, it is almost always the case that a negative HIV DUO test at 28 days or more will be conclusive and will not need repeating.

    6.I think this points to what you call if there is a human error that through must be another risk situation and have to repeat the test is the same as the 28 days and would be the antigen and igm?

    • Sebastian Rpo

      Dr excuse my bad English , the test gave negative and these are the questions of a product called Freedomhealth about the test at 28 days .

  42. I had protected vaginal sex with one highclass escort in India and kissing. I do not have open shores and cuts. Is there a risk of HIV or other STD .Do i need to go through tests than which tests.Please guide me.

    • I’m sorry. This forum is not for dispensing medical advice. Please see your doctor for what tests you need to do. All I can say is that you are at risk of HIV but the risk is very low. You are also at risk of other STDs.

  43. Sebastian Rpo

    Dr data to argue that combo is conclusive evidence is that IgM are in maximum blood at 24 days and p24 appears to 7 days , with this the 28th already a conclusive result . What is the reason you believe that BASH STATEMENT put a period of 8 weeks?

    • I think the recommendation to retest at 8 weeks is more to rule out human error than because of a concern of the accuracy of the test itself. Or maybe it is just for a “just in case so that we can legally cover our asses” reason. I’m not sure.

  44. Hello again the link works but the file u want to read is downloaded to your Downloads folder.For the link that u have sent to me i disearee about the holes in condoms.The holes in condoms does not exist,if they break they break obviously and u understand that u are in risk and should test.My condom has broken with my girlfriend and i have seen it how it breaks.Holes in condom does not exist and water test is in my opinion Bullshit sorry for this word.also one’s again the link : http://www.bashh.org/documents/BASHH-EAGA%20statement%20on%20HIV%20WP%20(Nov%20%2014).docx

    • Sebastian Rpo

      Here is the text for the link does not work:

      BASHH/EAGA statement on HIV window period

      November 2014

      HIV testing using the latest (fourth generation) tests is recommended in the BHIVA / BASHH / BIS UK guidelines for HIV testing (2008). These assays test for HIV antibodies and p24 antigen simultaneously. A fourth generation HIV test on a venous blood sample performed in a laboratory will detect the great majority of individuals who have been infected with HIV at 4 weeks after specific exposure.

      Patients attending for HIV testing who identify a specific risk occurring less than 4 weeks previously should not be made to wait before HIV testing as doing so may miss an opportunity to diagnose HIV infection (and in particular acute HIV infection during which a person is highly infectious). They should be offered a fourth generation laboratory HIV test and be advised to repeat it when 4 weeks have elapsed from the time of the last exposure.

      A negative result on a fourth generation test performed at 4 weeks post-exposure is highly likely to exclude HIV infection. A further test at 8 weeks post-exposure need only be considered following an event assessed as carrying a high risk of infection.

      Patients at ongoing risk of HIV infection should be advised to retest at regular intervals.

      Patients should be advised to have tests for other sexually transmitted infections in line with advice on window periods for those infections (see BASHH guidelines at: http://www.bashh.org ).

      Dr Keith Radcliffe – Chair, BASHH Clinical Effectiveness Group
      Dr Laura Waters – Chair, BASHH HIV Special Interest Group
      Prof Brian Gazzard – Chair, Expert Advisory Group on AIDS
      Dr Jan Clarke – President, British Association for Sexual Health and HIV

    • LOL! I think NIAID will be very upset you called bullshit on their study!

  45. Camilo Rpo

    Dr I value what you do for people helping them with this issue, first of all want to thank.
    Dr long before I was finding out when he did not know of your page, and I found something that I doubt genre and is a statement on BASH STATEMENT HIV window period 15th march 2010 where he said that despite the combo was very good at 28 days had to be repeated at 3 months, I wrote to a lab and they said it was because some subtypes of HIV and could not identify the so it was good to repeat at 3 months the 3rd generation, I want to ask if they have knowledge and this test has included all subtypes and me can do with ease the 28th since I live in Colombia and here make HIV architect combo Abbot?

    • Camilo Rpo

      It was already updated the text to November 2014, and says :A further test at 8 weeks post-exposure need only be considered following an event assessed as carrying a high risk of infection. That is for them a high risk referred to , that would apply in this case . if all risks are equal if they refer or if one was with hiv positive person identified , but if you do not know ?

      • I find the lab statement rather confusing. If there are subtypes of HIV that cannot be identified on tests, then why would repeating the test at 3 months make any difference? If the subtypes cannot be identified that logically they cannot be identified no matter how long you wait to take the test. I also think the recommendation to test at 8 weeks for a high risk infection is based more on the “just in case someone somewhere cocks it up” mantra rather than on the accuracy of the test itself.

  46. Sebastian Rpo

    Dr I value what you do for people helping them with this issue, first of all want to thank.
    Dr long before I was finding out when he did not know of your page, and I found something that I doubt genre and is a statement on BASH STATEMENT HIV window period 15th march 2010 where he said that despite the combo was very good at 28 days had to be repeated at 3 months, I wrote to a lab and they said it was because some subtypes of HIV and could not identify the so it was good to repeat at 3 months the 3rd generation, I want to ask if they have knowledge and this test has included all subtypes and me can do with ease the 28th since I live in Colombia and here make HIV architect combo Abbot?

    • BASH STATEMENT HIV WINDOW PERIOD has changed NOV 2014 from 12 weeks to 8 weeks 😉

      • Thank you for sharing. Can you put the reference link here please? Thanks!

        • http://www.bashh.org/documents/BASHH-EAGA%20statement%20on%20HIV%20WP%20(Nov%20%2014).docx .This is the link 😉 i tested with a DUO after 10 weeks post my last exposure negative 0.05(cutoff:0.25) and i had over 2 years lot of protected oral and protected sex.Also Condoms works when use consistently

          • And HIV cannot get through Latex,no way no how.For Chris’s sake always use a condom consistently for oral and vaginal and if u don’t have any breakage or slip,u can be confident that ur test will become negative.Peace all of you

          • I completely agree that everyone should use condoms correctly and consistently. However, there have been several studies to suggest that condoms may not be absolutely 100% effective. For example this report released in 2001 (http://www.niaid.nih.gov/about/organization/dmid/documents/condomreport.pdf) on page 14 it makes the statement “Overall, Davis and Weller estimated that condoms provided an 85% reduction in HIV/AIDS transmission risk when infection rates were compared in always versus never users.” So just let me say that I agree with you in that everyone should use condoms and based on the statistics, everyone who uses condoms correctly and consistently should not be worried just like you said. However, I would like to add that even if you use condoms all the time, it would be still prudent for you to get a HIV test every so often. Again, thank you for sharing.

          • Thank you very much for sharing. Unfortunately, for some reason, the link is not working. If it is not too much trouble could you put the link up again? I really appreciate this sharing of information. We can all learn much more about HIV.

        • Anxious

          Dear Dr Tan, bashh.org -> bashh guidelines-> bashh/eaga position statement on HIV window period 14 Nov 2014. It says 8 weeks need only be considered for a high risk of carrying infection. Does it means the new confirmatory test is 8 weeks?


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