There are a number of different HIV tests. Some of them are tests to find out if you have been infected with HIV. There are also two other main tests, the viral load test, and the CD4 count. These are tests which may be done when when you are taking HIV treatment.
Viral load test & CD4 count
The CD4 count is a test which measures how many CD4 cells an HIV positive person has in their blood. It effectively shows how well a person's immune system is functioning. A person's CD4 count should increase as a result of a person taking HIV treatment.
A viral load test is a way of checking if a person's HIV treatment is working. It is a way of measuring the amount of HIV there is in a cubic milliliter of blood. The lower the number the less HIV is in a person's body and the less damage it causes. When a person is taking antiretroviral treatment, the aim is to get the viral load count to undetectable levels. This means that a viral load test does not give a measurable result.
It doesn't however mean that there is no HIV in a person's body. HIV may still be in "sleeping" CD4 cells that cannot be reached by antiretroviral treatment. These cells are often referred to as the latent reservoir.
There are other HIV tests that can be used to find out if a person is infected with HIV.
Have you been infected with HIV?
The only way to find out if you have been infected with HIV is to have an HIV test. This is because symptoms of HIV infection may not appear for many years. If you think that there is a chance that you could have been infected with HIV you should arrange to have a test as soon as possible.
If you are infected the sooner you are diagnosed the sooner that you can start treatment for HIV. This means that you can avoid becoming seriously ill. Some HIV tests may need to be repeated 1-3 months after exposure to the virus but you shouldn't wait this long to seek help.
How are HIV tests done?
A test for HIV infection involves testing a sample of your blood or saliva. In most countries there are a number of different places where a test can be done. Sometimes a test can now be done in your home.
The different choices are:
Blood test - a sample of blood is taken in a clinic and sent for testing in a laboratory. Results are usually available within a few days.
Point of care test - a sample of saliva is taken from your mouth or a small spot of blood is taken from your finger. The sample doesn't need to be sent to a laboratory and the result is available within a few minutes.
Home sampling kit - you collect a saliva sample or a small spot of blood at home and send it off in the post for testing. You will be contacted by phone or text with your result or text with your result in a few days.
Home testing kit - you collect a saliva sample or small spot of blood yourself and test it at home. The result is available within minutes. If the test finds no sign of infection your result is "negative". If signs of infection are found the result is "positive".
The Window Period
The blood test done in a laboratory is the most accurate test and it normally gives reliable results from 1 month after infection has occurred.
The other tests tend to be less accurate and may not give a reliable result for a longer period after exposure to the virus. This period is known as the "window" period. For all these other tests a blood test should be carried out to confirm the result if the first test is positive.