In the early stages of infection, HIV often causes no symptoms and the infection can be diagnosed only by testing a person's blood. Two tests are available to diagnose HIV infection - one that looks for the presence of antibodies produced by the body in response to HIV and the other that looks for the virus itself.
Antibodies are proteins produced by the body whenever a disease threatens it. When the body is infected with HIV, it produces antibodies specific to HIV. The first test, called ELISA (Enzyme Linked Immunosorbent Assay), looks for such antibodies in blood.

If antibodies are present, the test gives a positive result. A positive test has to be confirmed by another test called Western Blot or Immunoflouroscent Assay (IFA). All positive tests by ELISA need not be accurate and hence Western Blot and repeated tests are necessary to confirm a person's HIV status. A person infected with HIV is termed HIV- positive or seropositive .

As ELISA requires specialized equipment, blood samples need to be sent to a laboratory and the result will be available only after several days or weeks. To cut short this waiting period, RAPID TESTS , that give results in 5 to 30 minutes, are increasingly being used the world over. The accuracy of rapid tests is stated to be as good as that of ELISA. Though rapid tests are more expensive, researchers have found them to be more cost effective in terms of the number of people covered and the time the tests take.

The HIV- antibodies generally do not reach detectable levels in the blood till about three months after infection. This period, from the time of infection till the blood is tested positive for antibodies, is called the Window Period . Some times, the antibodies might take even six months to show up. Even if the tests are negative, during the Window Period, the amount of virus is very high in an infected person. Hence, if a person is newly infected, the risk of transmission is higher.

If a person is highly likely to be infected with HIV and yet both the tests are negative, a doctor may suggest a repetition of the tests after three months or six months when the antibodies are more likely to have developed.

The second test is called PCR (Polymerase Chain Reaction), which looks for HIV itself in the blood. This test, which recognizes the presence of the virus' genetic material in the blood, can detect the virus within a few days of infection.

There are also tests like Radio Immuno Precipitation Assay (RIPA) , a confirmatory blood test that may be used when antibody levels are difficult to detect or when Western Blot test results are uncertain. Other available tests are Rapid Latex Agglutination Assay , a simplified, inexpensive blood test that may prove useful in medically disadvantaged areas where there is a high prevalence of HIV infection, and p24 Antigen Capture Assay .

The process of getting tested for HIV can generate a variety of intense emotional reactions such as fear, anger and denial. Therefore, psychological counselling is essential to prepare individuals undergoing testing for the possible consequences. This is called Pre-Test Counseling and is unavoidable for anybody preparing to take a test.

If the test result is positive, it should not be disclosed without another round of counseling. This Post-Test Counseling is more crucial because of the enormous stress and the multitude of emotions that the infected person could undergo on learning his/her HIV status. A positive test has been linked to increased suicide ideas and attempts and emotional trauma, both at the time of knowing the positive result and also at the emergence of AIDS-defining symptoms.

As there is still considerable stigma and discrimination attached to HIV/AIDS, the decision whether to test or not itself should be preceded by considerable introspection and assessment of the possible outcome. The person to take test should be aware of the emotional trauma and the possible consequences a positive test could bring about. For these reasonse, pre-test counseling is very crucial. With the help of the counselor, the person taking the test should assess his/her personal setting and prepare himself/herself for the probable consequences.

On the other hand, one should also be aware of the positive advantages of learning one's HIV status. If the test turns out to be positive, one can have early access to treatment, take care of one's health better and plan the future. Early realization of the health condition can be very useful in a large number of cases. The counselor could help the infected individual win back his/her confidence and learn how to live a healthy and responsible life. The individuals should also be prepared how to deal with their relatives, friends, colleagues, classmates etc. If the test is negative, the person should be advised preventive methods.