At a Glance
Why Get Tested?
To determine if you are infected with Human immunodeficiency virus (HIV)
When to Get Tested?
One month to three months after you think you may have been exposed to the virus (the average time for the antibody to be detected is two to eight weeks after exposure to the virus); once a year if you are at increased risk of being exposed to the virus; when your doctor thinks that your signs and symptoms may be due to HIV; before becoming pregnant or when pregnant
A blood sample collected from a vein in your arm; there are also tests available that can be performed on oral fluid.
Test Preparation Needed?
The Test Sample
What is being tested?
Human immunodeficiency virus (HIV) is the cause of AIDS (acquired immunodeficiency syndrome). This test detects antibodies produced in response to an HIV infection. The antibodies may be detected in blood or other body fluids, such as oral fluid or urine.
An HIV infection may initially cause no symptoms or cause flu-like symptoms that resolve after a week or two. This is followed by a simmering infection that may cause few symptoms for a decade or more. If the infection is not treated, eventually symptoms of AIDS emerge and begin to progressively worsen. Over time, HIV destroys the immune system and leaves a person's body vulnerable to debilitating infections. There are two types of HIV, 1 and 2. HIV-1 is the most common type found in the United States, while HIV-2 has a higher prevalence in parts of Africa.
When HIV enters the body, such as through exposure to the blood or body fluids of an infected individual or contaminated needle, the immune system responds by producing antibodies directed against the virus. These antibodies can be detected with screening tests about 2 to 8 weeks after exposure to the virus. If exposure to the virus is more recent, then antibody levels may be too low to detect and repeat testing at a later time may be required.
A few different options are available for HIV antibody screening. All HIV tests used in the U.S. detect HIV-1, and some types have been developed that can also detect HIV-2. Some versions can detect both HIV antibody and an HIV marker called the p24 antigen. Levels of p24 antigen are typically high early in the course of infection. An antibody/antigen combination test may be performed to increase the likelihood that HIV infection is detected sooner after exposure occurs.
Depending on the test, antibody screening may be performed on a sample of blood or oral fluid. The sample may be collected at a doctor's office or local clinic and sent to a laboratory for testing. Rapid antibody tests may be available in these settings and can provide results in about 20 minutes. Some tests are designed so that a sample can be collected at home and then sent to a laboratory. The Food and Drug Administration (FDA) approved in July 2012 a test for use at home. Though the test has limitations, the FDA felt the potential benefit of increasing the number of people tested for HIV outweighs the drawbacks of possible errors when the test is performed at home. (For more on this, see the article Home Testing: Avoiding Errors.)
Regardless of the type of antibody screening test used, a positive result requires follow up with supplemental testing to establish a diagnosis of HIV.
Detecting and diagnosing HIV early in the course of infection is important because:
- It allows for early treatment that slows progression to AIDS.
- An individual can learn of their status and modify behavior so as to prevent the spread of disease by not exposing others to their blood or body fluids.
- A pregnant woman can undergo treatment that would help prevent her spreading the disease to her child.
How is the sample collected for testing?
A blood sample is obtained by inserting a needle into a vein in the arm. There also are tests available that can be performed on oral samples. An oral sample is obtained by using a special small, spatula-like device with a flat pad on the end. The flat pad is placed above the teeth against the outer gum and is swabbed completely once around the outer part of the upper and lower gums.
NOTE: If undergoing medical tests makes you or someone you care for anxious, embarrassed, or even difficult to manage, you might consider reading one or more of the following articles: Coping with Test Pain, Discomfort, and Anxiety, Tips on Blood Testing, Tips to Help Children through Their Medical Tests, and Tips to Help the Elderly through Their Medical Tests.
Another article, Follow That Sample, provides a glimpse at the collection and processing of a blood sample and throat culture.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
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NOTE: This article is based on research that utilizes the sources cited here as well as the collective experience of the Lab Tests Online Editorial Review Board. This article is periodically reviewed by the Editorial Board and may be updated as a result of the review. Any new sources cited will be added to the list and distinguished from the original sources used.
Sources Used in Current Review
(© 1995-2012). Test ID: HIVE HIV-1/-2 Antibody Evaluation, Serum. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Clinical+and+Interpretive/9333 through http://www.mayomedicallaboratories.com. Accessed February 2012.
Mayo Clinic staff (2012 January 6). HIV testing. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/hiv-testing/MY00954/METHOD=print through http://www.mayoclinic.com. Accessed February 2012.
Bennett, N.J. and Gilroy, S. (Updated 2011 November 9) HIV Disease. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/211316-overview through http://emedicine.medscape.com. Accessed February 2012.
Bennett, N. (Updated 2011 July 14). Laboratory Assays in HIV Infection. Medscape Reference [On-line information]. Available online at http://emedicine.medscape.com/article/1995114-overview#showall through http://emedicine.medscape.com. Accessed February 2012.
Frequently Asked Questions. CDC National HIV and STD Testing Resources [On-line information]. Available online at http://www.hivtest.org/faq.aspx through http://www.hivtest.org. Accessed February 2012.
Keller, D. (2011 October 6). HIV Patients Treated Long-Term May Have False-Negative Tests. Medscape Medical News [On-line information]. Available online at http://www.medscape.com/viewarticle/751067 through http://www.medscape.com. Accessed February 2012.
Delaney, K.P. et. al. Performance of an alternative laboratory-based algorithm for HIV diagnosis in a high-risk population. J Clin Virol (2011), doi:10.1016/j.jcv.2011.09.013.
Masciotra, S. et. al. Evaluation of an alternative HIV diagnostic algorithm using specimens from seroconversion panels and persons with established HIV infections. J Clin Virol (2011), doi:10.1016/j.jcv.2011.09.011.
Wesolowski, L. et. al. Performance of an alternative laboratory-based algorithm for diagnosis of HIV infection utilizing a third generation immunoassay, a rapid HIV-1/HIV-2 differentiation test and a DNA or RNA-based nucleic acid amplification test in persons with established HIV-1 infection and blood donors. J Clin Virol (2011), doi:1016/j.jcv.2011.09.026.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 544-547.
Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 609-612.
(September 26, 2006) Centers for Disease Control and Prevention. Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Setting. MMWR 55(RR14);1-17. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5514a1.htm through http://www.cdc.gov. Accessed MayFeb 2012.
Qaseem A, et al. Screening for HIV in Health Care Settings: A Guidance Statement From the American College of Physicians and HIV Medicine Association. Ann Int Med, January 20, 2009 vol. 150 no. 2 125-131. Available online at http://www.annals.org/content/150/2/125.long through http://www.annals.org. Accessed April 2012.
Sources Used in Previous Reviews
Thomas, Clayton L., Editor (1997). Taber's Cyclopedic Medical Dictionary. F.A. Davis Company, Philadelphia, PA [18th Edition].
Pagana, Kathleen D. & Pagana, Timothy J. (2001). Mosby's Diagnostic and Laboratory Test Reference 5th Edition: Mosby, Inc., Saint Louis, MO.
Janice K. Pinson MT, MBA. Molecular Business Strategies, Birmingham, MI.
Pagana, Kathleen D. & Pagana, Timothy J. (© 2007). Mosby's Diagnostic and Laboratory Test Reference 8th Edition: Mosby, Inc., Saint Louis, MO. Pp. 23-27.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. Pp. 487-490.
Bennett, N. and Rose, F. (2008 October 22, Updated). HIV Disease. eMedicine [On-line information]. Available online at http://www.emedicine.com/med/TOPIC24.HTM through http://www.emedicine.com. Accessed on 10/26/08.
Mayo Clinic Staff (2008 August 9). MayoClinic HIV/AIDS. MayoClinic.com [On-line information]. Available online at http://www.mayoclinic.com/health/hiv-aids/DS00005 through http://www.mayoclinic.com. Accessed on 10/30/08.
(2005 November, Revised). Human Immunodeficiency Virus (HIV) Introduction. Merck Manual for Healthcare Professionals [On-line information]. Available online at http://www.merck.com/mmpe/sec14/ch192/ch192a.html?qt=HIV&alt=sh through http://www.merck.com. Accessed on 10/30/08.
(2008 September, Reviewed). Human Immunodeficiency Virus – HIV. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/InfectiousDz/Viruses/HIV.html through http://www.arupconsult.com. Accessed on 10/30/08.
(2006 September 22). Revised Recommendations for HIV Testing of Adults, Adolescents, and Pregnant Women in Health-Care Settings. CDC MMWR 55(RR14); 1-17 [On-line information]. Available online at http://www.cdc.gov/mmwr/preview/mmwrhtml/rr5514a1.htm through http://www.cdc.gov. Accessed on 11/1/08.
(January 29, 2009) OraSure Technologies. Oral Fluid—Specimen Collection and Testing Procedures. P. 4. PDF available for download at http://www.orasure.com/uploaded/400.pdf through http://www.orasure.com. Accessed February 2009.