Q. How sensitive is HIV 2 RNA PCR qualitative test?

Answered by
Dr. Purohit Manish
and medically reviewed by Dr. Vinodhini. J
This is a premium question & answer published on Dec 30, 2020

Hello doctor,

My question is related to HIV 2 RNA PCR qualitative test from a reputed lab. We presume that the qualitative test will answer as detected/not detected. But in this test, there is the issue of sensitivity limit as 100IU/ml, meaning that specimen having viral load < 100 copies/ml cannot be detected by this assay. How can a person with doubtful exposure of more than six months be sure that he is HIV 2 virus free from this test as he may be under that limit being less pathogenic virus and this test is rarely done in other labs. This test's quantitative limit is also 100 copies/ml.

Nowadays, Western blot tests had a lot of criticism due to reasons known to experts only. So how to resolve it since the HIV Duo screening test has numerical value problems and rapid tests is not accurate. For the HIV Duo test, after a window period of three months, the test shows reactive index values like 0.05, 0.2, 0.4, 0.6, 0.8, etc., with cut off as 1, i.e., as reactive. Please explain what does increasing order value means, i.e., more close to 1, meaning thereby more likely to develop HIV infection in the future or something else. How value between 0.9 to 0.99 to be interpreted as this is an equivocal value or needs retest? How 0.8 interpreted, which is close to 0.9? These thing creates confusion and needs detailed explanation before taking this test for sensitive and OCD nature person. HIV 1 DNA PCR done by lab gives clear cut detected /not detected, so there is no issue, but they are not doing HIV 2 RNA PCR nowadays. Please try to help me to come out of this HIV testing mess.



Welcome to

I can understand your concern and try to relieve your worry.

None of the tests having 100% sensitivity and specificity, every tests having some limitations. Therefore if there is any doubt, we need to do multiple tests. But in your case, you have elapsed more than six months of exposure. In this case, you can undergo HIV antibody testing as HIV antigen or PCR test is highly sensitive during the early period of infection. With the progression of time, their sensitivity decreases because the latent phase started. Again they come up during the last stage of the disease. Hence antibody testing for HIV is a reliable method after six month period.

For this testing, you can consult the ICTC center available all over the country, where they perform antibody testing and the positive result confirmed by three tests with a different principle.

Reactive index value signifies test is reactive or positive for antigen or antibody. Such tests are developed after a series of experimental studies over the positive and negative specimen to decide a cut-off value; therefore, the index value always indicates the true result. But as I said, every test has some limitations, so other tests should always be done for confirmation in case of a doubtful result. Further, these tests are based on the serological principle. In such a test, host immune response also participates in interfering with OD value therefore, only OD value above cut off should be considered a positive result.

If SRL is not doing PCR for HIV 2, there is no need to be a worry. You can consult in the ICTC center to undergo antibody testing for HIV 2 that is reliable at this stage.

Thank you doctor,

I received your reply and wanted to give you some more information that I could not answer in the previous question.

I had one lip kissing with my friend and one oral sex. After three months, I got done HIV 1 and 2 antibody test by CMIA method, and it was nonreactive. After that, after six months, I got done HIV fourth generation. Antigen and antibody test by CMIA and the result was nonreactive, and they do not give reactive index value and directly give result. They also follow the NACO protocol in reporting as others follow.

Now I just wanted to cross-check it with another lab, but they show reactive index value with cut-off value as 1. Being an OCD patient, if I get an index value as 0.8 or o.9. Will there be any reason to worry since the 0.9 value is taken as equivocal. However, the lab declares reactive or nonreactive, also in reporting. I also got done two rapid HIV tests, which are also more than six months, and both were negative for HIV 1 and 2 antibodies.

Shall I treat my HIV 1 DNA PCR qualitative and HIV 2 RNA PCR qualitative from reputed labs after quite a long window period? As being OCD, I take an annual screening combo test in the lab. Please reply to take further action.



Welcome back to

I have gone through your complete case report (attachment removed to protect patient identity) and giving my opinion in a single sentence that there is no need to worry. You can alleviate all your worries and survive a happy life.

As you have had a negative result from rapid test two times and fourth-generation ELISA and another test. We can consider it as conclusive evidence for the result.

Further, I wish to inform you that the sexual act you had performed carries a low risk for transmission of HIV, and also, HIV can be transferred from one person carrying HIV, not from all individuals. If you know your friend's HIV status, you can again be confirmed about your test result.

There is no need for repeated testing as you have undergone so many investigations so far. So, in my opinion, no further action is needed. However, as per the protocol, antibody testing can be done one year after exposure.

Thank you doctor,

As per your version, an antibody test after one year of exposure is a standard protocol. I have a query that protected and unprotected sex performed before a few years can have delayed antibody formation and may show results late at this stage since I have read that some persons have late or no seroconversion. Due to this reason, I had gone for DNA PCR qualitative test to confirm no virus itself, but it had sensitivity limitations in HIV 2 case. I had done the HIV fourth-generation test every year after exposure.

I am a chronic diabetic for the last 20 years and now on Insulin. In addition to this, I do take alcohol on alternate days as 100/150 ml for a long. I go for an annual checkup, and liver and kidney functioning is all within limits. Can this factor cause delayed antibody response since I keep on worrying about my previous years exposures? Please explain this issue since, as per your version maximum gap period is one year? What is the maximum window period defined in such situations? Please also explain my previous query of cut off value in the reactive index figure. Please explain in detail being sensitive and OCD in nature.



Welcome back to

If your all other systemic function test are within normal limits, then why are you worried. You should not think about previous exposure because if you have had any exposure to HIV, antibody development takes place within this time limit. Presently, all your investigations will favor nonreactive results. Therefore, you are not suffering from HIV infection.

I have already told you about the index value of the test. These values are standard and decided after several tests using the same kit and got validation. So there is no doubt about the test result. But for equivocal result or value near to positive cut-off, we always need to repeat the test using another method.

The maximum gap period is not one year, but it is a standard protocol to rule out infection possibilities. However, as per the literature, the window period for HIV is six months, and after this period antibody can be detected.

Thank you doctor,

This query is regarding the common myth that HIV infection cannot be passed via contaminated food items like fruit chat, salad, Pani puri, etc. Having HIV infected blood via a street vendor, restaurant waiter may not be visible to you.

CDC has also clarified that the HIV virus is very fragile gets inactivated when exposed to air, and stomach acid also kills it. It is generally said that the HIV virus does not survive long outside in the air, but it takes a few minutes, depending on the conditions. In this case, it is the winter season, and the temperature is around 10 degrees centigrade. So virus may be active for some duration, say a few minutes. You may please explain the survival time of the HIV virus concerning atmospheric condition and temperature.

A person taking cold salad (having carrot, beetroot, red onions, tomatoes, etc., where blood may not be separately distinct) have HIV infected blood from water in sufficient quantity in the salad but not visible, consumes it immediately after water cuts and serves to him. So there is no time gap.

The person eating this infected salad has very poor mouth hygiene, i.e., having large cuts, sores, bleeding gums inside his mouth. Now the fresh infected blood in salad interacts with blood coming in his mouth in bleeding gums, sores, etc., and makes it likely possible to reach in his bloodstream to cause HIV infection.

He might have some ulcers in his stomach track to further aggravate it, which is unknown. Although I am taking extreme situations, such may exist in real life. Please explain to me in detail the possibilities of passing HIV infection to the person eating that salad.

If yes, with what reasons, and if no, with what reasons. The query is because of OCD nature and so needs proper answer to get mental peace. What precautions should be taken by us while eating in dhabas, street chat vendors, etc.?



Welcome back to

These are hypothetical questions and not relevant to scientific literature. It is not possible to answer such a question on this ground. They are subjected to the research study. Further, the HIV gets inactivated within a few minutes, but there is no fixed period for it is inactivation in literature.

Thank you doctor,

My wife and I both are diabetic, and sometimes I inject Insulin into her. A few days back, I had a prick in my hand twice, and blood came out from her pen needle. It was twice in the last month. We both were tested in the previous year for an HIV combo test, and it was negative. We are both in monogamous relations; therefore, this finger prick from her pen requires HIV screening.

Please clarify whether HIV fourth-generation test from the lab requires cross-checking for reliability. Whether the card test is done in ICTC is reliable, and what are these tests' sensitivity and specificity? Whether only a card test is done in the reputed lab after six months for an HIV test is reliable, or shall we require any other test to rule out this possibility?

Some sites tell if you are sexually active, then yearly HIV screening is to be done. Whether this is applicable with single monogamous relations with wife also. What precautions should ladies take in beauty parlor when they use skin-piercing instruments? All parlors in colonies are not very hygenic, so shall one use their own such instruments in their kit to avoid blood born infections. Shall we worry when the lab's reactive index value shows 0.86 when the cut off is 1 in the HIV test? Kindly reply in detail to resolve my doubts.



Welcome back to

If you are in a monogamous relationship and know your HIV status, there is no need for HIV screening this time. No need to cross-check the fourth-generation ELISA result. HIV Card tests are reliable as these are highly sensitive, so the chances of missing positive cases are negligible. Card tests done after six months are reliable as these card tests detect antibodies against HIV. Six months is a sufficient period for antibody development.

No need for routine HIV screening in a person who is in monogamous relation. It is recommended for those sexually active persons who are having multiple sexual partners. Any instrument used in a beauty parlor for skin piercing or causes a breach in the skin during use should be sterilized using a chemical agent. Females can ask for these practices before use. If your parlor is not reliable and you wanted to take many precautions, you can use your own instrument. No need to cross-check if the reactive index is less than the negative value. I have also told you about this in my previous reply.

Thank you doctor,

One of my friends is HIV infected with poor mouth hygiene, i.e., have bleeding gums, sores, etc. Normally, we sit together in drinks and take snacks like chicken tikka, kabab, and paneer of big sizes and salad items like onion, carrot, beetroot, cucumber, and mooly, etc., are also big in size. As per his habit, he chews these items partially being big and then keeps them on the plate, mostly taken by me. There had been reports in the USA where infants infected with HIV via prechewed food given by caretakers who were HIV infected. So please explain whether such infection is possible in adults also and if so, then how and what precautions can be taken. If no, then with details. I want to know whether rapid card test reports at the ICTC center are reliable after six months, or do we require an HIV combo test to confirm it?



Welcome back to

These are hypothetical assumption which does not have any significance. Route of transmission of HIV may be sexual contact, injection of infected blood or body fluid, infected material goes into eye and from infected mother to child. So apart from these, all the causes are hypothetical. Therefore, I do not want to comment on anything else on this.

Rapid card tests are used to detect antibodies against HIV in the body, and these are reliable from ICTC. Antibodies develop in the body within two to eight months after infection. If you have any doubt, you can go for ELISA that is a more sensitive and specific method.

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