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Tests and diagnosis

By Mayo Clinic staff

HIV is most commonly diagnosed by testing your blood or saliva for the presence of antibodies to the virus. Unfortunately, these types of HIV tests aren't accurate immediately after infection because it takes time for your body to develop these antibodies — usually up to 12 weeks. In rare cases, it can take up to six months for an HIV antibody test to become positive.

A newer type of test checks for HIV antigen, a protein produced by the virus immediately after infection. This test can confirm a diagnosis within days of infection. An earlier diagnosis may prompt people to take extra precautions to prevent transmission of the virus to others.

Tests to tailor treatment
If you receive a diagnosis of HIV/AIDS, several types of tests can help your doctor determine what stage of the disease you have. These tests include:

  • CD4 count. CD4 cells are a type of white blood cell that's specifically targeted and destroyed by HIV. A healthy person's CD4 count can vary from 500 to more than 1,000. Even if a person has no symptoms, HIV infection progresses to AIDS when his or her CD4 count becomes less than 200.
  • Viral load. This test measures the amount of virus in your blood. Studies have shown that people with higher viral loads generally fare more poorly than do those with a lower viral load.
  • Drug resistance. This type of test determines if your strain of HIV is resistant to any anti-HIV medications.

Tests for complications
Your doctor might also order lab tests to check for other infections or complications, including:

  • Tuberculosis
  • Hepatitis
  • Toxoplasmosis
  • Sexually transmitted diseases
  • Liver or kidney damage
  • Urinary tract infections
Treatments and drugs Preparing for your appointment
References
  1. Basic information about HIV and AIDS. Centers for Disease Control and Prevention. http://www.cdc.gov/hiv/topics/basic/index.htm. Accessed May 18, 2010.
  2. HIV and its treatment: What you should know. AIDSinfo. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/HIVandItsTreatment_cbrochure_en.pdf. Accessed May 18, 2010.
  3. Kumar V, et al. Immunodeficiency syndromes. In: Kumar V, et al. Robbins and Cotran Pathologic Basis of Disease, Professional Edition. 8th ed. Philadelphia, Pa.: Saunders Elsevier; 2009. http://www.mdconsult.com/das/book/body/202273019-4/0/2060/57.html?tocnode=57529567&fromURL=57.html#4-u1.0-B978-1-4377-0792-2..50011-0--cesec96_437. Accessed May 18, 2010.
  4. Quinn TC. The global human immunodeficiency virus pandemic. http://www.uptodate.com/home/index.html. Accessed May 18, 2010.
  5. Opal SM, et al. Human immunodeficiency virus. In: Ferri FF. Ferri's Clinical Advisor 2010. Philadelphia, Pa.: Mosby Elsevier; 2009. http://www.mdconsult.com/das/book/body/202273019-4/1002085996/2088/313.html#4-u1.0-B978-0-323-05609-0..00017-4--sc0185_6437. Accessed May 18, 2010.
  6. Bartlett JG. The stages and natural history of HIV infection. http://www.uptodate.com/home/index.html. Accessed May 18, 2010.
  7. Opal SM, et al. Acquired immunodeficiency syndrome. In: Ferri FF. Ferri's Clinical Advisor 2010. Philadelphia, Pa.: Mosby Elsevier; 2009. http://www.mdconsult.com/das/book/body/202273019-4/1002085996/2088/22.html#4-u1.0-B978-0-323-05609-0..00010-1--s1620_340. Accessed May 18, 2010.
  8. Living with AIDS. Centers for Disease Control and Prevention. http://www.cdc.gov/hiv/resources/brochures/livingwithhiv.htm. Accessed May 19, 2010.
  9. Neurological complications of AIDS fact sheet. National Institute of Neurological Disorders and Stroke. http://www.ninds.nih.gov/disorders/aids/detail_aids.htm. Accessed May 21, 2010.
  10. Bartlett JG. When to initiate antiretroviral therapy in HIV-infected patients. http://www.uptodate.com/home/index.html. Accessed May 21, 2010.
  11. Side effects of anti-HIV medications: Health information for patients. AIDSinfo. U.S. Department of Health and Human Services. http://aidsinfo.nih.gov/contentfiles/SideEffectAnitHIVMeds_cbrochure_en.pdf. Accessed May 21, 2010.
  12. Eating defensively: Food safety advice for persons with AIDS. U.S. Food and Drug Administration. http://www.fda.gov/ForConsumers/ByAudience/ForPatientAdvocates/HIVandAIDSActivities/ucm135844.htm. Accessed May 21, 2010.
  13. Natural medicines in the clinical management of HIV/AIDS. Natural Medicines Comprehensive Database. http://www.naturaldatabase.com. Accessed May 21, 2010.
  14. The HIV/AIDS programs: Find HIV/AIDS care. U.S. Department of Health and Human Services. http://hab.hrsa.gov/findcare/index.htm. Accessed May 21, 2010.
  15. Fourth generation HIV diagnostic test approved, permitting earlier detection of infection. Food and Drug Administration. http://www.fda.gov/ForConsumers/ByAudience/ForPatientAdvocates/HIVandAIDSActivities/ucm216409.htm. Accessed June 24, 2010.
  16. FDA approves first-of-its-kind HIV test which can detect HIV days earlier than current U.S. tests. Abbott Laboratories. http://www.abbott.com/global/url/pressRelease/en_US/60.5:5/Press_Release_0875.htm. Accessed June 24, 2010.
  17. Daar ES, et al. Clinical presentation and diagnosis of primary HIV-1 infection. Current Opinion in HIV and AIDS. 2008;3:110.
  18. Sax, PE. Primary HIV-1 infection: Pathogenesis; epidemiology and clinical manifestations. http://www.uptodate.com/home/index.html. Accessed Oct. 17, 2011.
  19. Stages of HIV. U.S. Department of Health and Human Services. http://www.aids.gov/hiv-aids-basics/diagnosed-with-hiv-aids/hiv-in-your-body/stages-of-hiv/. Accessed Oct. 19, 2011.
  20. Fauci A, et al. Human immunodeficiency virus disease: AIDS and related disorders. In: Longo DL, et al. Harrison's Online. 18th ed. New York, N.Y.: The McGraw-Hill Companies; 2012. http://www.accessmedicine.com/resourceTOC.aspx?resourceID=4. Accessed Oct. 19, 2011.
DS00005 Oct. 20, 2011

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