Healthy Living

How is HIV Diagnosed?

How is HIV Diagnosed?

Key Takeaways

  • When you should test for HIV infection
  • Types of HIV tests

What is HIV and how is it diagnosed?

HIV refers to a virus and an infection that attacks the immune system. The virus is transmitted from one person to another by the sharing of body fluids. This can happen through unprotected sex, blood transfusion, or sharing of any piercing objects that might pass blood or fluids. Once a person gets the virus, it is difficult to detect what is happening during the first weeks. The infection affects the CD4+ cells in the body and starts replicating itself. However, the body reacts by producing antibodies.

When should I get tested for HIV?

  • If you have been having unprotected sex.
  • Men having sex with other men, especially with multiple partners and without a condom.
  • A person suffering from other sexually transmitted infections.
  • People injecting themselves with drugs.
  • If you have shared piercing materials with anyone.
  • People who have had accidents and have experienced intense bleeding.
  • If you had the test in the last 3 months and it came out negative. It is best to have yourself re-tested as it is difficult to identify the virus during the early stages of infection. The body always takes some time to produce antibodies after a person gets infected.

Types of HIV Tests

The common way of testing for HIV is through a blood test. A blood test will show if the immune system is producing antibodies to fight the virus. However, the fact that the body takes a long time to produce these antibodies, there’s a chance the results may not be fully accurate. There is a need to repeat the test multiple times for accurate results.

Early testing is also important in order to give the patient and the doctor enough time to discuss treatment options to prevent the development of the virus. If you think you’ve been exposed to the virus, have yourself tested immediately. During the first days of infection, the virus can be easily identified. 

Below are the methods used in testing for HIV.

      1.  ELISA Test

ELISA stands for “enzyme-linked immunosorbent assay.” ELISA test is one of the most common tests for HIV, and, as the name suggests, the test is linked to enzymes. The ELISA test targets the antibodies. However, the test may not be accurate during the first stages as antibodies may not be produced yet. If a patient tests negative in the first test, it is advisable to repeat the test after three months. If the patient tests positive in ELISA, a Western blot test follows to confirm the virus. The ELISA test is very sensitive to chronic HIV infection, but will give poor results when antibodies are not produced during the window stage of the infection. This means that the ELISA test can produce negative results during the early few weeks and months of the infection.

     2. Saliva Test

In this test, the saliva is taken to the lab for examination. To obtain the saliva, a cotton pad is passed over the surface of your upper or lower gum. The sample will then be placed in a vial and taken to the lab for examination. In case the results are positive - which usually comes in three days - a blood test will follow to confirm.

     3. Western Blot Test

This is a rare but very serious test. The Western blot test is done if the ELISA test comes out positive in order to confirm the infection.

     4. Home HIV Tests

Through advanced research and technology, two home tests for HIV have been discovered namely: oral quick home test and home access test for HIV using HIV-1 test system. The test kits for Home HIV tests can be bought at local chemists, but you should make sure that they are approved by the FDA. The available home tests for HIV are discussed below:

  • Oral Quick Test- This test involves oral administration of swab to generate fast results. You need to first swab your mouth with a certain oral fluid, and then take the fluid sample for testing using the HIV test kit. The results for oral quick test are available after ten minutes. If it comes out positive, you should go for a follow-up test. The manufacturers of these home test kits always provide confidential referrals and counselling. The principle behind this test is the antibody levels in the blood and swabbing fluid used. Since the level of antibodies is lower in the saliva or oral fluid compared to the blood, this test can find an infection later after exposure. It is therefore possible to get a false negative test with oral quick test. Up to 1 in 12 people may get false negative results with this test.
  • HIV-1 test system- This home access procedure allows you to take your blood sample at home. You can then send it to a licensed laboratory and call later to get your results. The whole procedure involves the use of a home collection kit to prick your finger and collect a blood sample. This test can be anonymous. If you get a positive result, a follow-up test should be performed immediately. The kit manufacturers will provide you with referral sites and confidential counselling.

    5.  Antigen/Antibody Combination Tests

This test can detect HIV virus as early as 20 days compared to the antibody test. It aims to detect HIV antigen and protein commonly known as P24. This protein is part of the HIV virus that can be detected 2-4 weeks after viral infection. Antibodies which act against this protein can also be detected 2-4 weeks after the infection. These rapid tests for antigen/antibody can provide HIV infection results within 20 minutes.

   6.  RNA Test

This is a special test which can be used to detect the virus itself. RNA test can help diagnose the virus approximately 10 days after exposure. This test is expensive, but it cannot be used as the first test for HIV. In case you are at high risk of getting HIV and you have symptoms related to flu, your doctor may go for this test.

   7.  Viral Load Test

This test is used to measure the amount of virus in your bloodstream. It is not usually used for diagnostic test but to monitor HIV treatment progress. Some recent technologies used to test the amount of virus in the blood include:

  • NASBA: Nucleic acid sequence-based amplification assay
  • RT-PCR: Reverse transcription polymerase chain reaction
  • bDNA: Branched DNA test

The principle behind these tests is similar, meaning any one test can be used to give results. However, the results may vary depending on the test used.

The Bottom Line

Most of the methods used to diagnose HIV cannot give accurate results especially at the early stages of the virus infection. Repeating the tests, especially if it's negative, is advisable. Other special tests, such as PCR test and RNA test, are advisable during HIV early stages test.