What is an ELISA test?

ELISA stands for enzyme-linked immunosorbent assay. It is an immunological test that helps to detect antibodies, antigens, proteins and glycoproteins present in blood. This test commonly used to detect human immunodeficiency virus (HIV) infection and pregnancy and to evaluate cytokines present in blood. An ELISA test is carried out on specialised surfaces to ensure that the antigen is firmly attached. Each ELISA kit is used to measure a specific antigen, and there are different kits for different antigens.

ELISA testing for HIV helps determine if the person is infected with HIV virus. HIV virus weakens and eventually destroys immune system, which leads to acquired immunodeficiency syndrome (AIDS). HIV testing is useful to slow the spread of HIV infection. Several individuals may be unaware that they could be infected with HIV. An early diagnosis warrants early treatment and control of infection.

The Centers for Disease Control (CDC) recommends that all people aged between 13 to 64 years should get themselves tested for HIV at community testing centres. HIV testing is highly recommended for pregnant women, as they can pass the virus to the foetus during pregnancy or to the newborn during breastfeeding.

  1. Why is ELISA test performed?
  2. How do you prepare for ELISA test?
  3. How is ELISA test performed?
  4. What do ELISA test results indicate?

ELISA is performed to detect certain viruses, bacteria or other infectious agents. It also helps to screen current or past infections. High-risk groups such as sexually active individuals should have an HIV test once a year or every 3 months, especially if they are having unprotected sex with multiple partners. HIV testing should also be considered prior to sexual intercourse with a new partner, if the individual:

  • Has had unprotected vaginal, oral or anal sex with more than one partner or with an unknown partner since last screening
  • Has a same-sex partner
  • Is using intravenous drugs, including hormones, steroids etc.
  • Has been diagnosed with a sexually transmitted infection, tuberculosis, hepatitis or syphilis
  • Has had unprotected sexual intercourse with a person belonging to any one of the above categories

A person should consider an ELISA test if they

  • Have been sexually assaulted
  • Plan to get pregnant or are pregnant

No special preparations are required for this test. One can avail home collection services for this test, or they can simply walk into a community testing centre. If the person has experienced problems, such as difficulty in giving blood; easy bruising; and a history of bleeding disorders, such as haemophilia or he/she is on blood thinner medications, they should inform the physician accordingly. Individuals with a fear of needles or those who faint at the sight of blood should also inform the laboratory technicians. They will take the necessary precautions to ensure the safety of the person.

ELISA for HIV testing is usually done by drawing a sample of blood from the arm. Sometimes, a swab is taken from cheeks to check cells for the presence of antibodies. Some individuals may feel a slight prick due to needle insertion. ELISA test takes about 5-10 minutes. A technician will explain the procedure, and the person may also be required to sign a consent form. After collection, the sample is sent to a laboratory for testing where the target antibody for HIV is to be detected. 

Normal results: Normal or negative results on the ELISA test for HIV indicate the antibody for HIV is absent in the blood. Negative result could be interpreted as no HIV infection or that the individual has been exposed to HIV but has not produced enough antibodies against HIV yet. Speak with your healthcare provider about the results obtained.

Abnormal results: An abnormal result or a positive ELISA test indicates that antibodies for HIV are present in the blood. This will need to be confirmed with further testing. A person with a confirmed positive HIV test will then be referred to an HIV clinic for further care.

Although there is no cure for HIV or AIDS, in the past few decades, medical treatment has highly advanced. HIV infection is now more easy to control, extending and improving the life of many. If HIV infection is well controlled, people can even have a normal life expectancy. Early diagnosis and treatment can delay the onset of AIDS. If a person is HIV positive, then his/her partner should equally be tested and treated for the same.

Disclaimer: All results must be clinically correlated with the patient’s complaints to make a complete and accurate diagnosis. This information is purely from an educational perspective view and is in no way a substitute for medical advice from a qualified doctor.

Lab Tests recommended for ELISA Test

Anti - ds DNA Antibody

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  1. Murray PR. The clinician and the microbiology laboratory. In: Bennett JE, Dolin R, Blaser MJ, eds. Mandell, Douglas, and Bennett's Principles and Practice of Infectious Diseases, Updated Edition. 8th ed. Philadelphia, PA: Elsevier Saunders; 2015:chap 16.
  2. National Health Service [internet]. UK; Diagnosis - HIV and AIDS
  3. Aoyagi K, Ashihara Y, Kasahara Y. Immunoassay and immunochemistry. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 44.
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