HIV Combo (Antigen And Antibody) Test

An HIV Combo (Antigen And Antibody) Test is an advanced (fourth-generation) screening test. It is used for simultaneous detection of HIV p24 antigen and antibodies to human immunodeficiency virus type 1 and type 2 (HIV-1/HIV-2) in blood. The test helps in the early diagnosis of an HIV infection. It does not distinguish between the detection of HIV p24 antigen, HIV-1 antibody, or HIV-2 antibody reactivity.

HIV attacks the body’s immune system and is transmitted through sexual contact with HIV-infected individuals. It can also spread by using infected needles or syringes, or from an infected mother to an unborn baby. If left untreated, it can lead to AIDS (acquired immunodeficiency syndrome).

During the first few weeks after exposure to the virus, the p24 antigen (HIV core protein) becomes detectable in blood. After 2-8 weeks, the body starts producing antibodies against this antigen. An HIV Combo (Antigen And Antibody) Test, also known as HIV Ag/Ab Combo assay, is a reliable way to check for HIV infection in early stages. The p24 antigen is the first marker of the presence of HIV in the body. Since the p24 antigen is usually detectable a few days before HIV antibodies, this test helps reduce the window period for HIV detection. The window period is the time immediately after infection when the test may not detect HIV antibodies or p24 antigens, possibly leading to a false-negative result.

An HIV Combo (Antigen And Antibody) Test is advised for people who are at an increased risk of HIV infection. These may include individuals who have an HIV-positive sex partner, have multiple sexual partners, are homosexual, and share needles frequently. The test may also be performed when there are symptoms like fever, chills, night sweats, muscle aches, oral thrush, sore throat, unintentional weight loss, swollen lymph nodes, mouth ulcers, etc. It should be noted that an individual may not show any symptoms if the infection is recent (or acute). Yearly screening is advised for those who are at high risk for HIV infection.

Fasting is not required before getting an HIV Combo (Antigen And Antibody) Test. This test can be scheduled as per individual convenience. A filled consent form for HIV testing and pre-test counseling (Annexure - CR/01) is required at the time of sample collection. The phlebotomist will provide this form before taking the sample. It includes the individual’s personal details, medical history, and pre-test counseling information. As per NACO guidelines, all reactive (positive) samples are tested using three different methods before issuing the final report. A Western blot test is used to confirm all reactive results.

HIV test results may vary slightly between different labs. The HIV Combo (Antigen And Antibody) Test uses an advanced, automated method called chemiluminescence immunoassay. This method checks for both HIV antibodies (types 1 & 2) and the p24 antigen. Depending on the lab and the machine used, the testing method (CMIA or CLIA) may differ. These fourth-generation tests are designed to detect both the virus (p24 antigen) and the body’s response (antibodies) in one test.

Lab test results require expert interpretation. Do not self-medicate at home solely based on these results, and always consult a doctor for a proper understanding of the test results.