At a Glance
Why Get Tested?
If you have been diagnosed with human immunodeficiency virus (HIV) and will be receiving anti-retroviral therapy, or if you are receiving anti-retroviral therapy that is not effective
When to Get Tested?
When first diagnosed with HIV and/or immediately prior to the start of anti-retroviral therapy, or if your HIV viral load rises steadily even though you are receiving anti-retroviral therapy
A blood sample drawn from a vein in your arm
Test Preparation Needed?
The Test Sample
What is being tested?
Resistance is a term used to describe the condition in which a microorganism is able to grow and/or multiply in the presence of one or more antimicrobial drugs. Human immunodeficiency virus (HIV) genotypic resistance testing evaluates the likelihood that the HIV strain infecting an individual has developed resistance to drug treatment.
Resistance can develop when antimicrobials are used to treat an infection and a mutation or change occurs in one of the microorganism's genes. This change leads to a mixed population in the infected person's body – some microorganisms that are drug-resistant, some that are drug-sensitive. Microorganisms without the mutation are killed, but those that have the mutation quickly multiply and begin to predominate. This is called "selective pressure" because the drug "selects" and allows the proliferation of the genetic forms of the microorganism that are resistant to it. When this occurs, the antimicrobial is no longer effective in treating the infection.
HIV mutates frequently – even in the absence of drug treatment – but not every mutation causes resistance. With genotypic resistance testing, the genetic code of the HIV a person has been infected with is analyzed to determine if there are any genetic mutations or changes that are known to cause anti-retroviral (ARV) drug resistance.
To avoid the development of ARV resistance, it is usually recommended that a person with HIV be treated with a combination of drugs that are from two different classes of ARV. This is known as highly active retroviral therapy or HAART. There are many different ARVs approved by the U.S. Food and Drug Administration that fall into different categories. For more on this, visit the National Institute of Allergy and Infectious Diseases web page on Treatment of HIV Infections.
How is the sample collected for testing?
The test is performed on a sample of blood drawn from a needle placed in the arm.
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.
Ask a Laboratory Scientist
This form enables you to ask specific questions about your tests. Your questions will be answered by a laboratory scientist as part of a voluntary service provided by one of our partners, American Society for Clinical Laboratory Science. If your questions are not related to your lab tests, please submit them via our Contact Us form. Thank you.
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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
(2011 January). Resistance Testing. U.S. Department of Health and Human Services Health Resources and Services Administration HIV/AIDS Bureau, Guide for HIV/AIDS Clinical Care [On-line information]. Available online at http://hab.hrsa.gov/deliverhivaidscare/clinicalguide11/cg-210_resistance_testing.html through http://hab.hrsa.gov. Accessed February 2012.
(Reviewed 2011 December 19). HIV Resistance Testing. AIDS InfoNet [On-line information]. Available online at http://aidsinfonet.org/fact_sheets/view/126?lang=eng through http://aidsinfonet.org. 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.
Hillyard, D. and Reimer, L. (Updated 2012 February). Human Immunodeficiency Virus 1, Antiretroviral Drug Resistance Testing - HIV Drug Resistance. ARUP Consult [On-line information]. Available online at http://www.arupconsult.com/Topics/HIVDrugResistance.html through http://www.arupconsult.com. Accessed February 2012.
(© 1995–2012). Test ID: GHIVR HIV-1 Genotypic Drug Resistance Mutation Analysis, with Reflex to Phenotypic Drug Resistance Prediction, Plasma. Mayo Clinic Mayo Medical Laboratories [On-line information]. Available online at http://www.mayomedicallaboratories.com/test-catalog/Overview/88782 through http://www.mayomedicallaboratories.com. Accessed February 2012.
Pagana, K. D. & Pagana, T. J. (© 2011). Mosby's Diagnostic and Laboratory Test Reference 10th Edition: Mosby, Inc., Saint Louis, MO. Pp 542-543.
Clarke, W., Editor (© 2011). Contemporary Practice in Clinical Chemistry 2nd Edition: AACC Press, Washington, DC. Pp 609-612.
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.
(Revised May 17, 2008) AIDS InfoNet. HIV resistance testing. Available online at http://www.aidsinfonet.org/fact_sheets/view/126 through http://www.aidsinfonet.org. Accessed February 2009.
Clarke, W. and Dufour, D. R., Editors (2006). Contemporary Practice in Clinical Chemistry, AACC Press, Washington, DC. P. 490.
(Oct. 30, 2008) Spacek lL. Johns Hopkins HIV guide, Resistance Testing: Genotype. Available online at http://www.hopkins-hivguide.org/management/laboratory_testing/resistance_testing__genotype.html through http://www.hopkins-hivguide.org. Accessed February 2009.
(Updated February 19, 2009) National Institute for Allergy and Infectious Diseases. Treatment of HIV Infections. Available online at http://www3.niaid.nih.gov/NR/exeres/A01539FA-7571-48C4-8A76-C526D5F7EFE9.htm through http://www3.niaid.nih.gov. Accessed February 2009.
(Updated November 3, 2008) AIDSinfo. Guidelines for the Use of Antiretroviral Agents in HIV-1-Infected Adults and Adolescents. Pp. 9-12. PDF available for download at http://aidsinfo.nih.gov/contentfiles/AdultandAdolescentGL.pdf through http://aidsinfo.nih.gov. Accessed February 2009.
(Update December 2008) International AIDS Society-USA. Update of the Drug Resistance Mutations in HIV-1: December 2008. Available online at http://www.iasusa.org/resistance_mutations/ through http://www.iasusa.org. Accessed February 2009.