HIV Testing - Everything you want to know

Before we begin, let’s make one thing clear that no single HIV test can provide an HIV-positive diagnosis. These tests are used in combination and in a specific sequence. 

HIV or Human Immunodeficiency Virus weakens the body’s immune system so that the infected person’s body is unable to fight even common germs, viruses, bacteria, etc. When a person gets sick because their immune system has stopped working due to HIV infection, they are said to have AIDS or Acquired Immune Deficiency Virus. 

There are a number of tests available today to check the spread of HIV. First, let’s understand some basics facts. 

Window period - When to get tested for HIV 

So you had unprotected sex, shared injecting equipment or think that infected blood has got into your body. Will testing for HIV the next day give you accurate results? The answer is no. You will have to wait for a window period – the time it might take for an HIV infection to surface. If a test is taken before window period, a person could be infected with HIV but still test negative. This window period is usually four weeks. 

So should you just wait and not visit the doc? 

No. In fact, just do the opposite. Visit a health professional within 72 hours of suspected infection. The doctors will take your history and check if you have a high risk of the infection and based on the assessment, may give you a course of PEP (post-exposure prophylaxis) to prevent infection. It is an emergency HIV treatment that will reduce your chances of being infected with HIV. 

You’ll be asked to come in for testing at a later date after your window period is over. Most modern HIV tests are now able to detect HIV from around four weeks after exposure. It is a good practice to be extra careful during your window period. Always use condoms and never share any injections because you are most infectious to others at this early stage of infection. 

Where can you get HIV testing

There are various ways of getting tested for HIV if you suspect that you have been exposed to the virus.

1. Private lab testing - You can get tested for HIV at various private laboratories like Dr. Lal Path labs, SRL Labs etc. 

2. Government hospitals -Many government hospitals provide free HIV testing. These test are done anonymously and the confidentiality of the person is maintained. Here are the names of government hospitals providing free HIV testing and counseling. 

3. Home-based testing kit - A quick internet search on home-testing kits in India reveals a number of kits which promise you accurate results in the comfort of your home such as Dr Trust HIV sure. However, we are not yet sure of how accurate these tests are or if they are approved by the government. In the US, two HIV home testing options have been approved by the Food and Drug Administration (FDA) – Home Access HIV-1 Test System and the OraQuick HIV test kit, but it is not yet available in India. 

4. Home-collection kit - The blood sample from a self-performed finger prick is sent to a laboratory. The results come in a few days. 

However, each of these ways of testing broadly comes under various types of HIV testing methods (given below). Which test is used on which person depends on the purpose and stage of testing for that person. Let’s find out more. 

Types of HIV testing

Rapid HIV Test – Rapid means fast. This test does exactly that – gives the results of the test faster – in 20 minutes. The test however needs to be done after the window period only. A person’s blood or oral fluid sample is taken to look for antibodies (protein produced by the body to fight diseases). However, if this test is conducted during the window period  (i.e., the period before the test can find antibodies), the test may give a false negative result. This type of test is useful for regular testing and is for those who want instant results from their evaluation. The accuracy level of the test is equal to that of a Standard Test.  

Standard Testing – This method to test for HIV is used is for routine evaluation or when the Rapid Test is not available. The results are delivered after four to five days of the submission of the blood or oral fluid sample. 

There are several kinds of standard tests. These include Antibody and Antigen tests. 

Early testing 

Viral load (RNA PCR) test

Also known as HIV I PCR Blood or HIV I, this test has shortest potential window and can be conducted between 9 to 11 days of suspected exposure. The RNA test looks directly for evidence of HIV RNA in the blood. If present, the results are positive. 

Results from RNA test are almost always reliable at 9 days following exposure, but it is recommended you wait until 11 days. However, the test may show different results if you have had flu or a shot of flu. It’s best to wait for  at least 4 weeks after vaccination/infection. 

However, this test is not recommended for HIV testing except in specific circumstances because they can give you false positive result. It is because of it’s sensitivity to detect traces of HIV RNA from your exposure even if you are not actually infected. 

It is recommended to take the HIV antibody test like ELISA (read below) after a few months of exposure to be sure of the results. ELISA will confirm if your body is producing all the antibodies it would need during an actual infection.

Antibody tests 

ELISA test  - The Enzyme-Linked Immunosorbent Assays or ELISA test is typically the first test ordered by a healthcare provider. It is one of the popular and highly effective antibody test. 

A positive result on this test does not necessarily mean that the person has HIV infection. The person can get a false positive result if he/she suffers from ailments like Lyme disease, syphilis, and lupus. If the result of the test is negative but there is a possibility of a recent exposure to HIV, the test must be repeated.

The ELISA test detects the presence of HIV virus by looking for antibodies that an infected person’s body produces against the HIV virus. The test must be taken 3-12 weeks from the suspected exposure to the virus. The test is conducted by collecting and testing a person’s urine, blood, saliva and other fluids of the mouth that contain antibodies. Tests done on blood samples can detect HIV sooner than those done on oral fluid samples.

The results of an antibody test may take a few days to arrive. However, a rapid version of antibody tests is also available, that can give results in under 30 minutes.

This test is also used to screen persons with low risk history, undergoing a periodic test to rule out HIV.

If the ELISA test is positive, it has to be followed by a Western blot test which then confirms an HIV infection and to begin an appropriate course of treatment. 

While the ELISA test may still be used in HIV screenings, the following tests could also be considered:

Antigen tests

Antigens are foreign substances that make the immune system act up. In case of HIV, antigens can be found in the body even before antibodies are released by the body. A specific antigen, a protein named p24, is looked out for to check for HIV infection. 

The window period for an antigen test is 2-4 weeks, i.e., an antigen test will confirm the presence or absence of HIV infection after this length of time.

An antibody test only looks for presence of antibodies that are produced by the body against presence of HIV virus in the body. An antigen test, on the other hand, will look for this protein, p24, that is a foreign body and is present in the HIV virus itself. 

Combination tests

A combination test searches the presence of, both, antigens and antibodies to ascertain HIV infection. Combination tests are also available in rapid version that can give the test-result in minutes. In the non-rapid form, combination test results take about the same time as the antibody tests.  Like antibody tests, combination tests are also popular for initial screening for HIV infection.

HIV test result positive - What next? 

People with positive results should opt for a second test. A second test helps in confirming the type of the infection and also the course of treatment. Some types of analysis following the infection test procedure are:

1. Western Blot Test 

A Western blot test is typically used to confirm a positive HIV diagnosis. A sample of blood is taken and checked to detect HIV antibodies, not the HIV virus itself. It is used to confirm a positive ELISA. The accuracy of both these combination tests is 99.9%. However, many physicians today do not use Western Blot test. Following a positive ELISA test, an HIV differentiation assay is done to confirm HIV infection. The provider may also order an HIV genetic material detection test.

2. Antibody differentiation test

This second type of test is done after an initial HIV antibody test result has come positive. The purpose of the testis to determine whether a person has HIV-1 or HIV-2. There are two types of HIV. Type I and Type II. Type I is more common in India. 

3. NAT or Nucleic Acid Testing 

This method is considered accurate during the early stages of infection, and can be used to find out the presence of HIV virus as early as within 10 days of the infection. This test looks for the presence of the virus itself, and can also tell about the amount of HIV virus present in the body, and in such a case is called viral load test. NAT is applied in only specific situations – person has had a high-risk exposure, has early symptoms of HIV, and so on. This test is also quite expensive, and so, only used in specific situations like the ones mentioned. RNA or Ribonucleic Acid is one kind of NAT.

4. CD4 count: 

CD4 cells are a type of white blood cell that are destroyed by the presence of HIV in a body. In a healthy person, the CD4 count can vary from anywhere between 500 to 1,000. It is important to note that HIV infection progresses to AIDS when a person’s CD4 count drops to 200. This can happen even when the person has no symptoms. So it is important for an HIV positive person to keep a check on CD4 count through regular tests. 

Cost and facilities for testing

• Each of these HIV testing methods require at least a few hundred rupees of spending, that can be a barrier to diagnosis and treatment. For this reason, for persons within reasonable or high risk of HIV infection, the government’s National AIDS Control Organisation (NACO) runs about 21,000 Integrated Counselling and Testing Centres (ICTCs), where the diagnosis is largely free of cost and is accompanied by counseling, that’s a very important part of HIV treatment. These facilities also provide first line of medication free of cost.
   

• ICTC is located in General OPDs, or Obstetrics and Gynaecology Departments of medical colleges or district hospitals or in maternity homes where everyone can access the service.
   

• The government also runs a national, toll-free helpline for information and assistance related to HIV and AIDS. It can be reached by dialing 1097 from any landline or mobile phone.
   

• Private facilities are known to turn away patients and not respect the patient’s consent on being tested or not, so government facilities are generally considered reliable for HIV testing. However, sometimes, practitioners at government facilities are also known to discriminate against people from non-binary sexual identities and other vulnerable people, even though NACO suggests action against such service providers. So, it’s important to know the processes and our rights to access these services as citizens.
   

It is important to remember that no method is without error, hence the need for repetition and double checking. One should not despair and take any extreme measures upon test results.

Please note – HIV infection does not always mean that you have AIDS. It is appropriate to wait for and understand the test results from a qualified, certified doctor/ medical practitioner and follow their advice for treatment to lead a smooth life.

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