[Question #1897] Hiv ag/ab combo abbot tests for p24,igg and igm?

Avatar photo
84 months ago

Hi doc I need  help on how the ag/ab combo from abbot diagnostic ci4100 test works and accuracy  . I tested for HIV  8months post exposure with negative result  and I have one exposure which was two years ago. Lab is clean and reputable saw abbot machine with my own eye 

Q1) tested after 8months some doc told me that  p24antigen drops and igm also drops after a few weeks .. But igg antibody remain present for life . Does the ag/ab combo from abbot check for igg antibody also ?

Q2) My test only said ag/ab combo assay for HIV 1/2. . I read the literature and could not find igg/igm anywhere only saw this line which said  "simultaneous detection of p24antigen and antibodies for  hiv 1/2 “ Why is that ? 

Q3) the test does not give me a separate result for p24antigen nor for igm and not even for igm antibodies Does it matter and why is that ? Lab said test isn't designed that way 

Q4) main question does it check both antibodies such as igg and igm even though I couldn't see it in the literature and lab supervisor said  we cannot give you separate results for p24 or igg and igm . 

Q5) my main fear is that due to p24antigen disappearing and igm also drops I am terrifed if I was tested for igm antibody or not ? 

 lab said  don't worry all antibodies are included in the test . The problem is even in broucher of the test they gave to me I could not find igg or igm anywhere . All it says is 

Simultaneous detection of p24antigen and antibodies HIV 1/2    It says nothing about igg or igm 

My test results look something like this 

Ag/ab combo    Result sco 0.16   That's a negative  

Abbot diagnostics ci4100 
If it's greater than 1.0 then it's positive 

Q6)All  I want to know does ag/ab combo tests from abbot diagnostics tests  for both antigen and all antibodies at the same time which is p24antigen and igg,igm antibodies for hiv1/2

Q7) does it matter that igg and igm are not written in the literature book the lab supervisor provided me .  

Q8) am I HIV negative ?  And they said this is totally computerised test with no human interference 

Q9) do you have the same test in your country ? 


Avatar photo
H. Hunter Handsfield, MD
84 months ago
Welcome to the forum. Thanks for your question.

You have become pretty knowledgeable about HIV antigen/antibody testing, probably through online research. However, I'm afraid you have misinterpreted some of what you have read and perhaps missed one crucial aspect. First, the antigen-antibody ("duo", "4th generation") HIV tests detect IgG as well as IgM antibody. Second and most importnat, it is the antibody that clears p24 antigen from the blood. After a few weeks, it is not possible to have antibody not appear (i.e. negative antibody component of the test) without the antigen component being positive. This is why the antigen-antibody tests are so good:  once positive, typically 2-3 weeks and always by 4 weeks after infection, the test is positive for life. There are no exceptions, or so few that this possibility can be entirely ignored. All the business you cite about IgG versus IgM antibody are irrelevant. The fact is that these tests are among the most accurate blood tests ever developed for any infectious disease, and your negative results prove for sure you did not catch HIV during the exposure 2 years ago that you are concerned about.

As I scan each of your individual questions, I think the above comments cover them all. I'll add that to my knowledge, the Abbott assay is identical and equally accurate in all countries world wide. The results are never reported as IgG or IgM specific. In fact, I believe the technologist doing the test cannot tell whether a positive result is based on IgG, IgM, or both -- and in any case it doesn't matter. 

So I think that covers it. You needn't be worried at all. But let me know if anything isn't clear.

Best wishes--  HHH, MD
Avatar photo
84 months ago
Thanks doctor but no I have zero knowledge that's why I just rushed to you I saw you on medhelp and you are award winning doctor and hugely respected 

Umm well doc soo just to be honest I was only worried because the when the lab manager gave me the literature book of abbot machine I started reading what the combo tests check for  just could not find the words igg and also igm 

However I did find words such as  simlatenous detection p24 antigen and antibodies HIV 1/2

1)The only worry I have is I was not able to see the igg and igm in literature I shouldn't worry it's irrelevant ? My tests checked everything nothing to worry about ? 

2)was my test ag/ab combo from abbot diagnostic ci4100 a  4th generation test ? 

3) basically doc I'm just worried that it checks for antigen and antibody and they are not designed to report seperate results that's fine isn't it ?  When it says simultaneous that means it's checking p24 antigen and checking igg igm antibodies ? 

4)Whenever I read the words ag/ab combo abbot diagnostic I should just think it checks for the antigen and all the relevant antibodies and my abbot diagnostic ag/ab combo is the test you say is conclusive at 4weeks ? Correct ? 

5)a negative test for HIV means a negative test for aids ? . Meaning god forbid if I had aids   I will always have positive HIV  test ? If you are negative for HIV then you are negative for aids also automatically?

6)I am truely HIV negative and also aids negative ? Meaning I don't have HIV and also aids 

Avatar photo
H. Hunter Handsfield, MD
84 months ago
Thanks for the additional information. But it does not change my opinions or advice.

1,2) Nobody "sees" IgG or IgM results on this test. There is no need, nor is there a rational reason for you to worry or be obsessed about it. And the antigen and antibody results also are not reported separately. If positive, either Ag or Ab is present, sometimes both. If negative, neither is present.

3) Yes. "ag/ab combo" and "4th generation" are exactly the same.

4) Repeat question. I already said your result was conclusive.

5,6) There is no lab test for AIDS, only for HIV. If you do not have HIV, you cannot have AIDS. In fact, HIV/AIDS specialists rarely even speak of "AIDS" any more. We speak of HIV infection, or of HIV/AIDS.

Each new question comes with replies to two follow-up questions or comments. Think carefully before you ask another question; it will be your last opportunity. Also please carefully re-read all my comments above before asking anything else. Most likely any additional concerns you have already have been answered.

Avatar photo
84 months ago
Thanks doc  I'll repeat unfortunately I went to my doc he said to say to keep it simple he Said this 

He said antigen means you are negative for p24antigen 
              Antibody HIV 1/2 means you are negative for antibody which includes igg and igm it's simple .  

In conclusion you are HIV and aids negative 

But I just want dr hunter handsfeild agree on this  would you agree with him ?  I think yes and no would do for this for additional peace of mind 

educational question 

Doctor I once had bad experience with blood drawing simply because person taking my blood said it was my responsibility to check needle and got scared about HIV 

But I  am bit low on confidence 

I always have a blood draw from butterfly needle which then connects to a vaccutainer 

My question is 

1)During the blood from vaccutainer  my arm creates negative pressure and blood flows out of my veins into the tube and into vaccutainer test tube does anything flow into my body during a blood draw ? 

2)does blood flow back into my vein after blood has been taken and test tube becomes full and vacuum in the test tube is finished 

2) I only have blood draw from one person after 6months because I just trust him and can't go to any other clinic 

3) if one got pricked by a needle after 7days from a butterfly needle can HIV live inside a butterfly needle and tube what are your views when does it normally die ? 

4) what are your views about this , some  say the virus dies after drying . I just want your general view and no other doctors view as to when HIV dies in a needle and tube . Is it hour or months what is the general idea about HIV survival in needles in the eyes of hunter handsfeild ?

Thanks doc and good I need your views on needle part and survival time will give me further knowledge I struggle to have blood draw form any other clinic. I always use needle which is manufactured atleast 2months before use because I think if HIV is in it HIV can't survive in a needle for 2months and gives me peace of mind . I want to have the courage to use a needle even if it's manufactured 2days ago . Thanks doc 

Avatar photo
H. Hunter Handsfield, MD
84 months ago
Your doctor said exactly the same thing I did in my replies above, so of course I agree.

1) No, the design of the Vacutainer and similar symptoms prevents any flow into the vein of the person having blood drawn. Also, the equipment is sterile, so even if this somehow could happen, there would be no infection risk.

2) This is irrational. Blood drawing never risks catching HIV or any other infection, and all blood drawing by any lab or technician is equally safe.

3) Butterfly needles are never re-used. However, if it had been re-used on an HIV infected person, then there would definitely be risk of catching HIV. But in the 3+ decades of the known worldwide HIV epidemic, this hasn't happened even once. It's a silly thing to worry about.

4) Because there have been no such transmissions, the biological reasons don't matter. HIV probably dies with drying, but there's really been little research on it.

All your comments suggest a potentially signficant mental health issue. If your irrational HIV/needle fears and compulsions about test interpretation are affecting your life as much as I suspect, or if you also have other fears of contamination that interfere with life and happiness, you should seek professional counseling. (For an excellent example of germophobia as an early sign of serious disability, see the movie The Aviator, about the billionair industrialist Howard Hughes. (It's a great movie, by the way.) I suggest all this from compassion not criticism.

That concludes this thread. Best wishes to you.