In general, testing for the human immunodeficiency virus (HIV) is a 2-step process that involves a screening test and follow-up tests. Show
How the Test is PerformedHIV testing can be done by:
SCREENING TESTS These are tests that check if you've been infected with HIV. The most common tests are described below. An antibody test (also called immunoassay) checks for antibodies to the HIV virus. Your health care provider may order the test for you to have done at a lab. Or, you may have it done at a testing center or use a home kit. These tests can detect antibodies starting a few weeks after you're infected with the virus. Antibody tests can be done using:
An antigen test checks your blood for an HIV antigen, called p24. When you're first infected with HIV, and before your body has a chance to make antibodies to the virus, your blood has a high level of p24. The p24 antigen test is accurate 11 days to 1 month after getting infected. This test is usually not used by itself to screen for HIV infection. An antibody-antigen blood test checks for levels of both HIV antibodies and the p24 antigen. This test can detect the virus as early as 3 weeks after getting infected. FOLLOW-UP TESTS A follow-up test is also called a confirmatory test. It is usually done when the screening test is positive. Several kinds of tests may be used to:
How to Prepare for the TestNo preparation is necessary. How the Test Will FeelWhen taking a blood sample, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away. There is no discomfort with an oral swab test or the urine test. Why the Test is PerformedTesting for HIV infection is done for many reasons, including for:
Normal ResultsA negative test result is normal. People with early HIV infection may rarely have a negative test result. What Abnormal Results MeanA positive result on a screening test does not confirm that the person has HIV infection. More tests are needed to confirm HIV infection. A negative test result does not rule out HIV infection. There is a period of time, called the window period, between HIV infection and the appearance of anti-HIV antibodies. During this period, antibodies and antigens may not be measured. If a person might have acute or primary HIV infection and is in the window period, a negative screening test doesn't rule out HIV infection. Follow-up tests for HIV are needed. RisksWith the blood test, veins and arteries vary in size from one patient to another, and from one side of the body to the other. Taking blood from some people may be more difficult than from others. Other risks associated with having blood drawn are slight, but may include:
There are no risks with the oral swab and urine tests. Alternative NamesHIV testing; HIV screening; HIV screening test; HIV confirmatory test Images
ReferencesBartlett JG, Redfield RR, Pham PA. Laboratory tests. In: Bartlett JG, Redfield RR, Pham PA, eds. Bartlett's Medical Management of HIV Infection. 17th ed. Oxford, England: Oxford University Press; 2019:chap 2. Centers for Disease Control and Prevention website. HIV testing. www.cdc.gov/hiv/guidelines/testing.html. Updated January 21, 2020. Accessed August 9, 2021. US Preventive Services Task Force; Owens DK, Davidson KW, et al. Screening for HIV infection: US Preventive Services Task Force recommendation statement. JAMA. 2019;321(23):2326-2336. PMID: 31184701 pubmed.ncbi.nlm.nih.gov/31184701/. Review Date 6/20/2021Updated by: Jatin M. Vyas, MD, PhD, Associate Professor in Medicine, Harvard Medical School; Associate in Medicine, Division of Infectious Disease, Department of Medicine, Massachusetts General Hospital, Boston, MA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. What tests are used to diagnose HIV?HIV Tests for Screening and Diagnosis. Antibody tests detect the presence of antibodies, proteins that a person’s body makes against HIV, not HIV itself. Most rapid tests and home tests are antibody tests. An initial HIV test usually will either be an antigen/antibody test or an antibody test.
How long does it take for a nucleic acid test to detect HIV?A nucleic acid test (NAT) can usually detect HIV 10 to 33 days after exposure. If you get an HIV test after a potential HIV exposure and the result is negative, get tested again after the window period for the test you took. Learn more about what a negative test result means.
What is HIV testing and why is it important?1 DEN-EN CHOFU University. HIV testing plays a crucial role in detecting and monitoring HIV infection. Diagnosis of HIV infection is basically made by sequential two tests: a screening test with an enzyme immunoassay (EIA) and a confirmatory test with Western blot.
What is a NAT test for HIV?NATs look for the actual virus in the blood. This test is very expensive and is not routinely used for HIV screening unless the person recently had a high-risk exposure or a possible exposure with early symptoms of HIV infection. A NAT can usually detect HIV infection 10 to 33 days after an exposure.
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What type of anticoagulant is generally suitable for TDM Analysis The single best answer heparin EDTA citrate oxalate?When considering therapeutic drug monitoring (TDM), heparinized plasma is generally suitable for most drug analyses.
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