If anHIV infectionhas been confirmed, tests are routinely performed to determine the status of a person’s immune system and the level of viral activity in the body.These are expressed in what is known as yourCD4 countandviral load.
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What Is a CD4 Count?
The CD4 test is one of the more familiar testing assays known to people with HIV. The test measures the level ofCD4 helper T-cellsin the blood—cells that are not only vital to immune function but are the primary target of HIV infection. As HIV gradually depletes these cells, the body becomes less able to defend itself against a widening range of opportunistic infections.
Normal CD4 counts are anywhere between 500-1,500 cells/ µL. Conversely, a CD4 count of 200 cells/ µL or less is technically classified asAIDS.
Previous treatment guidelines recommended thatantiretroviral therapy (ART)be initiated in patients with a CD4 count under 500 cells/µL or in the presence of anAIDS-defining illness. In 2016, updated guidelines from the World Health Organization endorsed ART in all HIV-infected patients, irrespective of CD4 count, location, income, or stage of disease.
Today, the CD4 count is used to predict disease outcome as much as to measure an individual’s relative immune strength. By way of example, theCD4 nadir(the lowest point to which the CD4 count has dropped) is predictive of long-term morbidity, with lower values suggesting an increased risk of HIV-related and non-HIV-related illnesses, as well as slower immune recovery.
What Is a Viral Load?
While the CD4 count is an indicator of immune status and treatment efficacy, the viral load is arguably the more important measure when antiretroviral therapy begins.
The viral load measures the concentration of virus in the blood, also known as your “viral burden.” Labs will use a genetic testing technology—typically, the polymerase chain reaction (PCR) or a bDNA (branched DNA)—to quantify the number of viral particles in a milliliter (mL) of blood. HIV viral loads can range from undetectable (below the detection levels of current testing assays) to the tens of millions.
An undetectable result does not mean there is no virus in your blood or you have been “cleared” of infection.Undetectable simply means that the virus population has fallen below testing detection levels in blood but may be detectable elsewhere, such as in the semen.
Goals of Viral Suppression
The aim of antiretroviral therapy is to achieve viral suppression, defined as having fewer than 200 copies of HIV per millilter of blood.
On the other hand, an increase in the viral load can often be an indication of treatment failure, poor drug adherence, or both.
That said, incidental variations in viral load (or “blips”) can occur even among those with 100% adherence. These are usually minimal and should not be the cause for alarm.
Benefits of Viral Control
According to research from the U.K. Collaborative Cohort Study (UK CHIC), people with undetectable viral loads who achieved a CD4 count of 350 cells/µL or more within a year of starting therapy were likely to have a normal life expectancy.
A 2013 retrospective study conducted at the University of Montreal monitored 1,357 HIV-positive men from 1999 to 2011, further demonstrated a virologic failure rate of nearly 60% in persons with persistent viral loads of between 500 and 999 copies/mL.
8 SourcesVerywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.U. S. National Library of Medicine, MedlinePlus.CD4 lymphocyte count.Lamp K, McGovern S, Fong Y, et al.Proportions of CD4 test results indicating advanced HIV disease remain consistently high at primary health care facilities across four high HIV burden countries.PLoS One. 2020;15(1):e0226987. doi:10.1371/journal.pone.0226987Bray S, Gedeon J, Hadi A, et al.Predictive value of CD4 cell count nadir on long-term mortality in HIV-positive patients in Uganda.HIV AIDS (Auckl). 2012;4:135–140. doi:10.2147/HIV.S35374National Institute of Allergy and Infectious Diseases.10 things to know about HIV suppression.CDC.HIV Treatment as Prevention.New York State Department of Health AIDS Institute, Clinical Guidelines Program.Virologic and immunologic monitoring.May M, Gompels M, Sabin C.Life expectancy of HIV-1-positive individuals approaches normal conditional on response to antiretroviral therapy: UK Collaborative HIV Cohort Study.J Int AIDS Soc. 2012;15(Suppl 4):18078. doi:10.7448/IAS.15.6.18078Laprise C, de Pokomandy A, Baril JG, Dufresne S, Trottier H.Virologic failure following persistent low-level viremia in a cohort of HIV-positive patients: results from 12 years of observation.Clin Infect Dis.2013 Nov;57(10):1489-96. doi:10.1093/cid/cit529Additional ReadingBaligh Y Fleishman J, Metlay J, et al.Sustained viral suppression in HIV-infected patientsreceiving antiretroviral therapy.The Journal of the American Medical Association; 308(4):339-342.Lundgren JD, Babiker AG, Gordin F, et al. Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med. 2015;373(9):795-807. doi:10.1056/NEJMoa1506816U.S. Department of Health and Human Services (DHHS).Guidelines for use of antiretroviral agents in HIV-infected adults and adolescents.AIDSinfo Update.
8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.U. S. National Library of Medicine, MedlinePlus.CD4 lymphocyte count.Lamp K, McGovern S, Fong Y, et al.Proportions of CD4 test results indicating advanced HIV disease remain consistently high at primary health care facilities across four high HIV burden countries.PLoS One. 2020;15(1):e0226987. doi:10.1371/journal.pone.0226987Bray S, Gedeon J, Hadi A, et al.Predictive value of CD4 cell count nadir on long-term mortality in HIV-positive patients in Uganda.HIV AIDS (Auckl). 2012;4:135–140. doi:10.2147/HIV.S35374National Institute of Allergy and Infectious Diseases.10 things to know about HIV suppression.CDC.HIV Treatment as Prevention.New York State Department of Health AIDS Institute, Clinical Guidelines Program.Virologic and immunologic monitoring.May M, Gompels M, Sabin C.Life expectancy of HIV-1-positive individuals approaches normal conditional on response to antiretroviral therapy: UK Collaborative HIV Cohort Study.J Int AIDS Soc. 2012;15(Suppl 4):18078. doi:10.7448/IAS.15.6.18078Laprise C, de Pokomandy A, Baril JG, Dufresne S, Trottier H.Virologic failure following persistent low-level viremia in a cohort of HIV-positive patients: results from 12 years of observation.Clin Infect Dis.2013 Nov;57(10):1489-96. doi:10.1093/cid/cit529Additional ReadingBaligh Y Fleishman J, Metlay J, et al.Sustained viral suppression in HIV-infected patientsreceiving antiretroviral therapy.The Journal of the American Medical Association; 308(4):339-342.Lundgren JD, Babiker AG, Gordin F, et al. Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med. 2015;373(9):795-807. doi:10.1056/NEJMoa1506816U.S. Department of Health and Human Services (DHHS).Guidelines for use of antiretroviral agents in HIV-infected adults and adolescents.AIDSinfo Update.
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read oureditorial processto learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
U. S. National Library of Medicine, MedlinePlus.CD4 lymphocyte count.Lamp K, McGovern S, Fong Y, et al.Proportions of CD4 test results indicating advanced HIV disease remain consistently high at primary health care facilities across four high HIV burden countries.PLoS One. 2020;15(1):e0226987. doi:10.1371/journal.pone.0226987Bray S, Gedeon J, Hadi A, et al.Predictive value of CD4 cell count nadir on long-term mortality in HIV-positive patients in Uganda.HIV AIDS (Auckl). 2012;4:135–140. doi:10.2147/HIV.S35374National Institute of Allergy and Infectious Diseases.10 things to know about HIV suppression.CDC.HIV Treatment as Prevention.New York State Department of Health AIDS Institute, Clinical Guidelines Program.Virologic and immunologic monitoring.May M, Gompels M, Sabin C.Life expectancy of HIV-1-positive individuals approaches normal conditional on response to antiretroviral therapy: UK Collaborative HIV Cohort Study.J Int AIDS Soc. 2012;15(Suppl 4):18078. doi:10.7448/IAS.15.6.18078Laprise C, de Pokomandy A, Baril JG, Dufresne S, Trottier H.Virologic failure following persistent low-level viremia in a cohort of HIV-positive patients: results from 12 years of observation.Clin Infect Dis.2013 Nov;57(10):1489-96. doi:10.1093/cid/cit529
U. S. National Library of Medicine, MedlinePlus.CD4 lymphocyte count.
Lamp K, McGovern S, Fong Y, et al.Proportions of CD4 test results indicating advanced HIV disease remain consistently high at primary health care facilities across four high HIV burden countries.PLoS One. 2020;15(1):e0226987. doi:10.1371/journal.pone.0226987
Bray S, Gedeon J, Hadi A, et al.Predictive value of CD4 cell count nadir on long-term mortality in HIV-positive patients in Uganda.HIV AIDS (Auckl). 2012;4:135–140. doi:10.2147/HIV.S35374
National Institute of Allergy and Infectious Diseases.10 things to know about HIV suppression.
CDC.HIV Treatment as Prevention.
New York State Department of Health AIDS Institute, Clinical Guidelines Program.Virologic and immunologic monitoring.
May M, Gompels M, Sabin C.Life expectancy of HIV-1-positive individuals approaches normal conditional on response to antiretroviral therapy: UK Collaborative HIV Cohort Study.J Int AIDS Soc. 2012;15(Suppl 4):18078. doi:10.7448/IAS.15.6.18078
Laprise C, de Pokomandy A, Baril JG, Dufresne S, Trottier H.Virologic failure following persistent low-level viremia in a cohort of HIV-positive patients: results from 12 years of observation.Clin Infect Dis.2013 Nov;57(10):1489-96. doi:10.1093/cid/cit529
Baligh Y Fleishman J, Metlay J, et al.Sustained viral suppression in HIV-infected patientsreceiving antiretroviral therapy.The Journal of the American Medical Association; 308(4):339-342.Lundgren JD, Babiker AG, Gordin F, et al. Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med. 2015;373(9):795-807. doi:10.1056/NEJMoa1506816U.S. Department of Health and Human Services (DHHS).Guidelines for use of antiretroviral agents in HIV-infected adults and adolescents.AIDSinfo Update.
Baligh Y Fleishman J, Metlay J, et al.Sustained viral suppression in HIV-infected patientsreceiving antiretroviral therapy.The Journal of the American Medical Association; 308(4):339-342.
Lundgren JD, Babiker AG, Gordin F, et al. Initiation of antiretroviral therapy in early asymptomatic HIV infection. N Engl J Med. 2015;373(9):795-807. doi:10.1056/NEJMoa1506816
U.S. Department of Health and Human Services (DHHS).Guidelines for use of antiretroviral agents in HIV-infected adults and adolescents.AIDSinfo Update.
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