[Question #4476] Is one Combi test enough?

30 months ago
Hi doctor.. Thanks for your information, support, and advice.

I don't want to waste your time with repetitive questions, so i have the following questions in mind and appreciate if i can have brief answers. 

1- If Combi tests are good enough, accurate, and cheap after 4 weeks, why would someone be referred to have a PCR which is much expensive?

2- Are confirmatory tests required? Don't Combi tests alone do the job?

3- I had a 30 mins unprotceted oral encounter 3 months back. I tested negative before a week (after 84 days)  in HIV Combi (I&II Antibodies+ P24 Antigen) Elisa, method: ECLIA. Result: 0.16 and negative is below 0.9 and positive above 1. Is one test enough? And does the method name affects the test accuracy as there are many combi tests like: CLIA, CMIA, etc...

4- Let's suppose the result is 0.8, does this mean a confirmatory test is important then? Whether by PCR or WB, etc...?

5- The Combi test i did was around 40$ (i did it in the UAE). To your knowledge, is this is really only the price of such a test that detects a virus like HIV?

Appreciate your time to answer such questions even in brief. But i feel many people have those questions in mind but rather keep repeating and asking the same always.

Thank you doctor.
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
30 months ago
Welcome to the forum. Thanks for your question.

Once in a while, enough information is provided in the title the user assigns to the question. That may be the case here. As I type this, I have not yet read beyond the title "Is one Combi test enough?" The answer is yes, as long as enough time has passed since the last possible exposure to HIV. That time is 4 weeks for 98-99% certainty and 6 weeks for a 100% conclusive result. So if you have been tested beyond those times, you can be confident you do not have HIV, no matter how high risk the exposure and no matter what symptos you might have.

Now I have read the rest of your question. Guess what? The quick reply to question 3 is that your negative result is conclusive and for sure you did not catch HIV during the exposure you are concerned about. But you also ask excellent questions about how people use the HIV blood tests, interpretation of results, and so on. So here are my thoughts. This may be more detailed than you expected; I'm using this an an opportunity for a blog-like reply that might be useful for future replies as well.

1) The DNA/RNA tests (PCR and related methods) have two main uses. First, to assess how advanced HIV is in people known to be infected, i.e. measuring the amount of HIV in the blood. Second to check for very early infection, before the AgAb (duo, combo, combi, etc) or antibody-only tests become positive. For example, all donated blood is so tested, in case a donor was exposed recently and might be in the window before other tests are positive; and after very high risk exposures. However, many anxioius persons request such testing despite low risk exposures. It's really not an appropriate use of these tests, but it's very common in people who are frightened and looking for earlier reassurance than provide by AgAb tests. The test is NOT recommended for the purpose you mention:  if an AgAb test is negative after 6 weeks (or antibody alone after ~8 weeks), doing a PCR is usually unnecessary and a waste of money.

2) Those comments answer this question. You are sort of right:  RNA/DNA testing always is done after a positive AgAb test, but the purpose is not confirmation of the result, but to determine the HIV blood level.

3,4) The numerical result is meaningless as long as it is below the cut-off for a positive result. With rare exceptions, when the cut-off ELISA ratio is 0.9, for example, results of 0.1, 0.4, 0,6, or 0.8 all are equally negative. The numerical result is unrelated to the amount of antibody or antigen in the blood, and the very same specimen tested 10 times will produce 10 different numerical results.

5) I have no information about the costs of testing outside the US, espeically in UAE or elsewhere in the Middle East, Africa, Asia, etc. In general, the tests are less expensive in developing than industrialized countries. $40 doesn't strike me as unusual, but I can't say more than that.

Thanks again for the insightful questions. I hope these commens are helpful. Let me know if anything isn't clear.

HHH, MD
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30 months ago
Thank you Dr. Handsfield for the ellaboration. That was really helpful and relieving. Reading over the internet and asking mis-informed doctors is the worst enemy in such cases. 

I don't think I have much more to ask as Dr. Hook and you had covered everything in the threads whether here or in Medhel, but i would like to make sure of:

1- Is there a possibility for an error (human or else to give false negative or positive) in the 4tg Generation Combi test? I recall you said earlier it's never wrong. 

2- I have a concern regarding STDs, I believe I'm fine but can't be sure. Almost 2-3 weeks after the encounter (my only encounter) i had a transparent or watery viscous penile recharge after uniration (i don't think it's the first time i see that) and think it's because of stopped any kind of sexual activities suddenly. No sores on penis or an abvious burning sensation at all (saw that recharge for few times in 2 months period). Plus, there is a slight feeling of ball in my throat which mostly is due to anxiety as i know. Can both things be due to anxiety and stopping any kind of sexual thinking/activity for a period of time? 
Do you suggest testing for any STD, knowing that they can have no symptoms.


Thank you again Dr. Handsfield. The effort and time you give use is really preciois. 
H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
30 months ago
1) The lab procedures for the HIV blood tests are highly automated and pretty much foolproof. Lab errors are virtually unheard of.

2) These symptoms are not suggestive of any STD. The only one that comes close is the occasional discharge. You mention urination, but I wonder whether you might have also defecated at the same time? Stool passing over the prostate and seminal vesicles (where semen is stored) sometimes squeeze out fluids. In any case, many men experience occasional clear mucus, especially early the day. Often it is pre-ejaculate fluid left over from natural erections that occur when dreaming. But without continuous discharge and/or pain on urination, almost always this isn't an STD symtpom. Your other symptoms indeed sound like physical manifestations of anxiety, especally the sensation of a "ball" or fullness in the throat. (It's so common it has a medical name, globus sensation. You can google it for more information.)

You don't given enough information for me to judge whether STD testing would be a good idea. Not on the basis of your symptoms, but you haven't described the sexual encounter you are concerned about. If it included unprotected vaginal, anal, or oral sex, it's possible you were at risk. IIf so, a urine gonorrhea/chlamydia test and a syphilis blood test mgith be warranted.
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30 months ago
It's the same encounter in my first reply, unprorected oral from a girl (20 mins) with a cunnilinctus (4 sec) and then stopped. She tested negative for HIV in a combo test for work after 30 days, and I didn't notice any kind of sores or anything that would grap attention in her. 

It waq my only encounter ever and was unplanned so was followed with guilt.  The fact that I'm married and was sexually active with my wife then had to stop for sometime plus anxiety may be reasons for the discharge as I was told, and there was no defacation as far as I can remember (and i had the discharge for only 4 or 5 times in different period, days or weeks between them).

As this is my last reply here due to the limitations, thank you again Dr. Handsfield for your ellaborations, effort, and patience. It's always good to hear from experts like you.

Best regards,

H. Hunter Handsfield, MD
H. Hunter Handsfield, MD
30 months ago
Thanks for the clarification; we've addressed the low risk for the oral sex encounter 3 months ago.

Also thanks for the kind words about our services. I'm glad to have hellped.
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