CD4/CD8 ratio

The CD4/CD8 ratio is a reflection of immune system health. A normal ratio is between 1 and 4. People without HIV infection generally have a greater number of CD4 cells than they have of CD8 cells. As people get older, the immune system's defence against pathogens is weaker and the CD4/CD8 ratio tends to decrease. People with autoimmune diseases tend to have an increased CD4/CD8 ratio, while those with viral infections have a decreased ratio.

Within six months of seroconversion, the CD4 count generally decreases about 30% and the CD8 count may increase by about 40%, resulting in an inverted ratio that is generally less than 1. With antiretroviral treatment, the ratio may revert toward 'normal'. Long-term non-progressors and those who start antiretroviral treatment early on generally have a normal CD4/CD8 ratio.

Factors affecting CD4 count and subsequently the CD4/CD8 ratio are some viral infections, tuberculosis, corticosteroid use, seasonal/diurnal variations, and variations in CD4 analyses.

Although not too much attention is paid to ratios now, one study found that the only independent predictors for immune reconstitution inflammatory syndrome (IRIS) were a low baseline CD4 count and a low CD4/CD8 ratio. Those people with a CD4/CD8 ratio of less than 0.15 were more likely to have an IRIS event than were people with a ratio greater than 0.30.1   

In Zimbabwe, a study was designed to evaluate the CD4/CD8 ratio as a predictor of HIV infection in infants under the age of 18 months. Whole blood samples from over 130 children were analysed using flow cytometry; PCR DNA testing was used as a control reference. A CD4/CD8 ratio <1 identified 75 of the 76 infants (median testing age 5.5 months) found to be HIV-positive by PCR DNA. Sixty out of the 61 infants who were PCR negative had a CD4/CD8 ratio ≥1. When the same technique was used in 250 HIV-positive adults, 249 had a CD4/CD8 ratio of <1. 2

Overall, the CD4/CD8 ratio had ≥ 98.7% sensitivity and 98.3% specificity for identifying infant HIV-1 infection (all subtype C) and 100% sensitivity and specificity when looking only at the 12 to 18 month infant subset. Similar results have been found in other studies.3 4


  1. Ratnam I et al. Incidence and risk factors for immune reconstitution inflammatory syndrome in an ethnically diverse HIV type-1-infected cohort. Clin Infect Dis 42: 418-427, 2006
  2. Zijenah LS et al. T lymphocytes among HIV-infected and -uninfected infants: CD4/CD8 ratio as a potential tool in diagnosis of infection in infants under the age of 2 years. J Transl Med 3:6, 2005
  3. Moodley D et al. Lymphocyte subset changes between 3 and 15 months of age in infants born to HIV-seropositive women in South Africa. Trop Med Int Health 2:415–421, 1997
  4. Embree J et al. Lymphocyte subsets in human immunodeficiency virus type 1 infected and uninfected children in Nairobi. Pediatr Infect Dis J 20:397-403, 2001
Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.