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Human Immunodeficiency Virus (HIV) is the cause of AIDS (Acquired Immuno Deficiency Syndrome). The presence of HIV in the body can be detected in several ways. The most common is the HIV-ELISA Antibodies test.
The HIV-ELISA looks for the body response to the virus manifested by the presence in your blood of Antibodies to HIV proteins. Antibodies are special proteins that our Immune System produce in response to the presence of HIV.
The test performed on your sample actually consists of two tests: a Screening test and a Confirmatory test. The screening test procedure is called an ELISA—Enzyme Linked Immuno-Sorbent Assay or an EIA (Enzyme Immunosorbent Assay). The confirmatory test is used in the event your HIV-ELISA is positive and/or equivocal and is the procedure used is the Western Blot Assay (WB)
The screening and confirmatory tests are usually done using small samples of blood. If a sample of blood tests positive repeatedly in the screening test, it will be confirmed through the Western Blot test. People will be informed that they are infected with HIV only after both the screening and confirmatory tests have shown a positive (reactive) result.
Positive HIV antibody tests results are over 99% accurate when confirmed. Negative HIV antibody tests are over 99% accurate if it has been at least six months after a contact with a potentially HIV-infected partner. False negatives or false positives occur rarely.
Antibodies to HIV can be detected in the blood, in the urine or in the saliva. People produce antibodies with different speeds and therefore the time interval between infection and the development of antibodies to HIV can go from four weeks to six months from the exposure date or SDC ( Suspected Date of Contact). The appearance of antibodies in a blood or urine sample of a person which was known to be negative to HIV is called Seroconversion.
The HIV Elisa results are usually available in one or two business days.
THE WINDOW PERIOD
The time period between a person’s contact with the virus (infection) and when HIV antibodies become detectable in blood or other fluids is called the "window period". Most people will develop antibodies detectable within 4-6 weeks after infection with HIV. Some people may take longer; but nearly all (99%) will have antibodies by 6 months following infection. Therefore, the test may not be accurate if a person gets tested too soon after a potential exposure. People waiting six months from the time of the exposure before testing will have a 99% accurate test result. Until now there have been no studies showing antibodies present in people with longer than six months exposure to HIV.
In 1986, a second virus causing the acquired immunodeficiency syndrome (AIDS), human immunodeficiency virus type 2 (HIV-2), was discovered and found to be relatively common in parts of West Africa. Because HIV-2 infections are not always detected by HIV-1 antibody tests, antibody tests for HIV-2 have been developed. Voluntary screening for HIV-2 antibodies by blood banks is a current acceptable practice. public health Department Clinics now use a HIV1 and HIV2 Elisa test.
Although most HIV infections in the United States are of HIV-1 group B subtype, current ELISAs can accurately identify infections with nearly all non-B subtypes and many infections with group O HIV subtypes. Infections with HIV-2 and HIV-1 group O are rare in the United States and routine screening for these subtypes is not generally recommended as part of diagnostic testing except in areas where several such infections have been identified. Routine screening for HIV-2 might be appropriate in certain populations where potential risk for HIV-2 infection is higher (e.g., in areas where West African immigrants have settled). Since June 1992, FDA has recommended routine screening for antibody to HIV-2 (in addition to HIV-1) for all blood and plasma donations. Clients with clinical, epidemiologic, or laboratory history that suggests HIV infection and negative or indeterminate HIV-1 screening tests should receive further diagnostic testing to rule out HIV infection, potentially including testing for HIV-1 non-B subtypes and HIV-2.
Blood centers can accomplish this either by the use of a single combination test for HIV-1/HIV-2 or by the use of two independent tests, one for HIV-1 and one for HIV-2. Screening donated blood and plasma for HIV-2 infection raises issues concerning appropriate strategies for testing for both viruses, HIV-2 testing in other settings, and notification of HIV-1 and HIV-2 test results. What follows are CDC recommendations for the diagnosis of HIV-1 and HIV-2 infections in persons being tested in settings other than blood centers and CDC/FDA guidelines for serologic testing with combination HIV-1/HIV-2 screening ELISAs.
Although HIV-2 appears to have spread in West Africa primarily via heterosexual transmission, HIV-2 infection has been reported in Europe in homosexual men, injecting drug users (IDUs), transfusion recipients, and men with hemophilia. HIV-2 is endemic in parts of West Africa and has also been reported in other parts of Africa. Apparently as a result of links with former colonies in West Africa, Portugal and France have reported the highest number of cases of HIV-2 infection in Europe. As of late 1989, 12.6% of AIDS cases in Portugal were caused by HIV-2. Although most of these cases were in persons originally from Africa, HIV-2 is also present among persons in Portugal with no known contacts with Africa. HIV-2 infection has also been reported in India.
In the Western hemisphere, rare cases of HIV-2 infection have been reported from Brazil, Canada, and the United States. Within the United States, CDC and others conduct surveillance for HIV-2, including serologic surveillance of blood donors and populations at increased risk of HIV-1 infection.
Since 1987, 32 persons with HIV-2 infection have been reported in the United States. Fifteen of these 32 were identified by serologic surveillance, and 17 were identified by case reports. Twenty-eight were residing in the northeastern United States, a frequent destination for West African immigrants and the area that has been most intensely surveyed using HIV-2-specific tests. No cases of HIV-2 infection have been reported among persons known to be IDUs or men reporting homosexual contact. More than 2,700 serum specimens that were reactive by HIV-1 EIA and indeterminate by HIV-1 Western blot have been tested for HIV-2 by either the New York City Health Department or the Maryland Department of Health and Mental Hygiene. HIV-2 infection was detected in specimens from 11 persons. The Massachusetts Department of Public Health identified two HIV-2-positive specimens among blood samples from 14,779 childbearing women. Positive HIV-2 specimens were detected among sera from two of 19,504 clients of sexually transmitted disease clinics, but in none of the specimens from 6,547 IDUs at drug-treatment centers. In other studies of populations at increased risk for HIV-1 infection, no cases of HIV-2 infection have been reported. Of 15 U.S. residents found to be positive for HIV-2 infection through serologic surveillance, demographic information was available for seven; six were West Africans and one was the U.S.-born wife of an HIV-2 infected West African.
Counselors are available on 1-866-478-3417
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