HIV Test: How to Interpret the Results

The HIV test is performed with the aim of detecting the presence of the HIV virus in the body and must be carried out at least 30 days after exposure to risky situations such as unprotected sex or having come into contact with the blood or secretions of people with HIV virus.

The HIV test is simple and is performed mainly through the analysis of a blood sample, but saliva can also be used to verify the presence of the virus in the body. All HIV tests investigate the two types of viruses, HIV 1 and HIV 2.

It is recommended to perform the test 1 to 3 months after the risk behavior, because the body takes more or less this time to replicate the virus in sufficient quantity to be detected in the HIV test, before this period The result can give a false negative.

How to Interpret the Results

To understand the result of the HIV test, it is important to verify whether it is reactive, non-reactive or undetermined, in addition to the values it indicates, since normally the higher the value, the more advanced the infection is.

HIV Blood Test

The blood test for HIV is performed with the objective of identifying the presence of the virus and its concentration in the blood, giving information about the stage of infection. The HIV test can be performed through several diagnostic laboratory methods, the ELISA method is the most widely used. The possible results are:

Reagent: It means that the person was in contact and was infected with the HIV virus;
Non-reactive: It means that the person is not infected with the HIV virus;
Indeterminate:  It is necessary to repeat the test because the sample was not clear enough. Some situations that can cause this type of result are pregnancy or having a recent vaccination.

In the event that the result of HIV positive the laboratory itself uses other methods to confirm the presence of the virus in the body such as Western blot, Immunoblot, Indirect immunofluorescence for HIV-1. So the positive result is really reliable.

Some laboratories also indicate a quantitative value in the HIV test, in addition to the reactive, non-reactive or undetermined result. However, this value does not have as much clinical importance as regards the determination of the test result, being only of medical interest. In case the clinician considers that it is an important value, he may request more specific tests such as the viral load test, where it is quantified in how much the virus is in the blood.

The test should be done 30 days after the risk behavior and, if the result is undetermined or non-reactive, it is recommended that the test be repeated after 60 days to verify the presence or absence of the virus. It is important to repeat the test so there are no associated symptoms such as rapid weight loss, fever, persistent cough, headache and appearance of red spots or small wounds on the skin. Know the main symptoms of HIV.

Rapid HIV Tests

The results of rapid tests that use a small saliva sample or a small drop of blood to identify the HIV virus and are ready in 15 or 30 minutes are also reliable, presenting concrete results. So the possible results are:

Positive: Indicates that the person has the HIV virus but the ELISA blood test should be performed to confirm the result;
Negative: Indicates that the person is not infected with HIV.

Rapid tests are used on the street, in government campaigns, in care and counseling centers for people with HIV / AIDS, and in pregnant women who begin labor without having had prenatal control. Like the blood test, it must be done 30 days after having the risk behavior.

These rapid HIV tests can also be purchased online or even in some countries already available at pharmacies. The form of use depends on the test since some use a drop of blood and others a swab that is rubbed into the gums to obtain a sample of the saliva. Some examples that have been approved by the FDA are OraQuick, Orasure, Autotest, and Mylan Autotest HIV.

What is the Viral Load Test?

The viral load test is a test indicated by the doctor when HIV infection is diagnosed, with the aim of monitoring the evolution of the disease. This test verifies the number of copies of the virus that is present in the blood at the time of collection. This test is requested 2 to 8 weeks after diagnosis to verify the initial viral load and is repeated every 3 months, in order to know if the indicated treatment is being effective or should be altered. 

When the viral load increases, it means that the infection has worsened and possibly there is a resistance of the organism to the treatment, so the doctor must change the therapeutic strategy. When the opposite happens, that is, when the viral load decreases over time, it means that the treatment is being effective, inhibiting virus replication.

When the result of the viral load indicates that it is undetermined, it does not mean that the disease has been cured, but that the virus is in very low concentrations in the blood, indicating that the treatment is being effective. There is a consensus of the scientific community that when viral load tests are undetectable, there is less risk of sexually transmitting the virus, however, the use of condoms during sexual intercourse is recommended.

When the Result can be a False Negative

The false-negative result can occur when the person performs the ELISA test or rapid tests in the first 4 weeks after the risk behavior. This occurs because the body takes 1 to 3 months to produce enough antibodies that can be detected by the HIV test.

However, even if the test has been carried out 1 month after the risk behavior, it can take up to 3 months for the body to produce enough antibodies against HIV and there may be a positive result. Therefore, it is important that the test be repeated 90 and 180 days after the risk behavior to confirm the presence or absence of the HIV virus in the body.

Basically, provided a positive result, there is no doubt that the person has HIV, while in the case of a negative result, it may be necessary to repeat the test due to a possible false-negative result. However, an infectologist can indicate what to do in each case.