HIV Testing

Pruebas VIH

Table of contents

HIV stands for human immunodeficiency virus. Many people refer to it as AIDS, but they do not mean the same thing. The term AIDS (acquired immunodeficiency syndrome) is the cause of HIV, which occurs if it is not treated. There is no 100% certain cure for HIV today. Thus, once an individual is infected, he or she is infected forever. This does not mean that he or she cannot enjoy a normal, healthy lifestyle. For its detection, the relevant HIV tests are carried out, which will be explained below.

How do you get HIV?

The most common way of contracting HIV is through unprotected sex. If one partner has contracted the virus, he or she can use effective treatments to have safe sex. Other routes of contamination would be through contact with the blood of an HIV-positive individual and during pregnancy, childbirth or breastfeeding through the mother to the baby. 

For an untreated individual with HIV, the virus usually develops fully in 3 phases:

  1. Acute HIV infection. This is the time when symptoms develop and infection begins. Patients experience a very high increase of HIV in their blood, making them extremely infectious.
  2. Chronic HIV infection. During this period the blood levels of the virus decrease, so do the symptoms. The duration of this phase can last for years, up to a decade even, if appropriate drugs are not administered. Once this phase is over, the viral load increases again, so the body moves on to phase 3.
  3. (AIDS) Acquired Immunodeficiency Syndrome. This is the phase we try to avoid, as it is the most serious. If the patient reaches this point, his immune system is so weakened that all kinds of opportunistic infections can affect him. Current medical advances have ensured that cases in which the patient reaches stage 3 are rare.

There are currently two different types of virus: HIV-1 and HIV-2. The fundamental difference is that the second one has a slower evolution in the organism and is less aggressive. The possibility of infection is therefore also reduced. This is the serotype that causes the global AIDS epidemic. HIV-2 is indigenous to West Africa.

Both HIV-1 and HIV-2 are transmitted in the same way. It is worth mentioning that HIV-2 sexual transmission is approximately 5 times less than HIV-1. Another common characteristic is that both types of HIV attack the patient’s immune system, weakening it against external aggressions. Without adequate treatment, the life expectancy of an individual with AIDS is approximately 3 years.

Types of tests

The difficulty in detecting HIV lies in the fact that there is a period of time, from the time the patient is exposed to HIV until it is detected, when the virus cannot be detected by any test. This time is known as the window. It is also not possible to detect how long ago a person was infected. 

HIV testing can tell us whether or not a person is infected. If so, the body generates an antigen, p24, which can be detected. This is created even before the production of antibodies, which is why it is essential to test for HIV. There are 3 types:

  • Antibody test. This is the most frequently performed test for HIV diagnosis. The objective is to detect antibodies against HIV-1 and HIV-2 in blood by enzyme immunoassay technique. Antibodies are proteins created by our own body to fight HIV. The problem, as we have mentioned before, of detection is the window period. The earlier the virus is detected the better, but since seroconversion does not occur until at least 4 weeks after contact with HIV, HIV testing can be compromised. Mention should be made of cases of individuals who are seronegative due to natural immunological causes and may still be infected with HIV.

If the test result is positive, it should be checked by immunoblotting.

  • Antibody test (confirmation). If the antibody test is negative, a confirmation test, also known as immunoblotting, must be performed. This detects antibodies to p31, p24 and p17 (HIV 1+ 2) antigens (recombinant proteins). It also detects antibodies to sgp 105 and gp36 (HIV-2) glycoproteins (synthetic peptides) in venous blood.
  • HIV-1 and HIV-2 RNA quantification. By means of quantification, the viral load of the 2 serotypes can be measured. A real-time polymerase chain reaction, also known as RT-PCR, is performed. It is the technique that can detect the virus the earliest (10 to 33 days prior to exposure to HIV). In addition, it is capable of detecting its presence even at very low concentrations.

Reliability of HIV test results

Depending on the type of HIV testing and the time in which it is performed, the reliability of the test may be compromised. The most reliable would be RT-PCR (by immunoblotting), as it could be detected within 10-33 days of exposure. Antigen testing would be from 18 to 45 days and antibody testing from 23 to 90 days. It also depends a lot on the patient’s organism, since each one has a unique and personal window period.

However, if there is a high risk of contact, it is recommended to retest after the window period, even if the result was negative the first time.

Risks of the test

Only a small amount of blood is needed for HIV testing, so the risks of testing are minimal. Slight bleeding, bruising from the needle stick or fainting may occur.

Is there a rapid HIV test?

Similar to the rapid test for COVID, the HIV rapid test is a self-diagnostic test sold in pharmacies. A small prick of the finger is used to obtain a blood sample for testing.

Today we can find in our pharmacies 2 types of tests. The first one detects only antibodies and must be performed at least 3 months after the possible infection. The second detects, in addition to antibodies, the HIV-1 p24 antigen. The window period of the second test is shorter. However, the HIV rapid test is currently the least reliable test available.

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