How does an HIV test work?
An HIV test is a blood test that is used to confirm or exclude an HIV infection. It is often colloquially referred to as an AIDS test. However, since the test detects the pathogen, i.e. the HI virus, the term HIV test is more correct.
Normally, doctors do not look directly for the HI virus in the blood, but for the cells that the immune system produces in response to it. This is a so-called indirect test procedure, by which the HIV infection can be confirmed or not. Two tests are done for a definite diagnosis of HIV: an antibody test and an antigen test.
First test for antibodies
In the first test, doctors have the patient’s blood tested for antibodies to the HIV virus. The body begins to produce such antibodies two to ten weeks after infection. However, they can only be detected in the blood after three months. If antibodies against the HI virus are present, the test result is positive.
Second test for antigens
After a positive test result in the first detection, doctors have a second test performed for confirmation. Here, antigens of the virus are detected in the patient’s blood. Antigens are protein structures of the virus against which the antibodies are directed. If there is actually an HIV infection, the test shows a positive result six weeks after infection.
Only if both tests are positive in a patient is he or she considered HIV-positive. It usually takes a few days until the test result is ready.
HIV test by PCR
Sometimes the tests for antibodies and antigens are inconclusive. In these individual cases, doctors have the HIV infection detected directly in the blood in the laboratory. This is possible via special genetic material components of the virus, which doctors call nucleic acids (HIV RNA). The search for this viral genetic material is carried out by means of an HIV PCR test.
PCR stands for polymerase chain reaction. In this procedure, the nucleic acids are first amplified and then broken down according to their properties.
HIV self-test for home
HIV tests for home use are also available. The advantage is that they are uncomplicated and can be performed anonymously. In many cases, this lowers the inhibition threshold for such tests. In addition, they are just as conclusive as a test at the doctor’s office. All you need is a little blood from your finger, which you put into the testing device. The result is obtained in just a few minutes.
One disadvantage of the procedure is that there is no personal consultation beforehand. In case of a positive test result, there is no immediate professional support on site. If your test result is positive, visit your family doctor or an AIDS counseling center to discuss how to proceed.
A positive self-test result does not establish a diagnosis of HIV; it is imperative that further testing be done to confirm with a physician. In addition, false positive results are common with HIV self-tests. Again, antibodies to HIV are only detectable in the blood after about three months, a negative test is accordingly also only meaningful then.
Where and at what cost is an HIV test possible?
The right places to go to get an HIV test done then are:
- Public health offices
- AIDS counseling centers
- General practitioners
- Various medical specialists, such as gynecologists
Doctors in medical practices usually have the HIV antibody/antigen tests performed by a laboratory. There the examination of the taken blood samples takes place. This HIV test in the laboratory does not exclude an infection until six weeks after the suspected infection. If there is a well-founded suspicion of an HIV infection, the health insurance company usually covers the costs.
Health offices or AIDS counseling centers also offer the HIV test in the laboratory, but usually also a rapid test. The result of the rapid test is usually available within minutes or a few hours. Often the HIV tests are available there free of charge or for a smaller amount of money.
In addition, there is also the possibility to get a self-test in the pharmacy, in the drugstore or online. Here, too, the result is available after just a few minutes. The costs of this type of HIV test are on average around 20 euros.
Also anonymous possible
In many European countries, HIV is one of the notifiable diseases, but this reporting is done anonymously, sometimes in a coded way. In this way, countries get an overview of the spread of the disease.
When is an HIV test useful?
If one fears to have been infected at a certain point in time, a test only makes sense three weeks after this event. This is because antibodies will have formed by then at the earliest. The body needs about two to ten weeks to produce antibodies against the HI virus and only then are they detectable in the blood.
If you have a well-founded suspicion that you have been infected with HIV, you should also visit a doctor or a counseling center before these three weeks have elapsed. This will provide you with all the important information and support you need in this situation.
Using a blood donation as an HIV test?
HIV testing procedures have been routinely used in Europe since about 1985 prior to donating blood. This usually helps to prevent people from becoming infected with HIV via a blood transfusion.
For this reason, it is more advisable to have this done directly at appropriate trained offices, for example at the health office or AIDS counseling centers. HIV testing and AIDS counseling there are anonymous and usually also free of charge.
