CD4 cell counts in the age of antiretroviral therapy

While viral load and CD4 cell count are both predictors of disease progression in untreated populations, there is evidence that CD4 cell count response on treatment is a better predictor of clinical outcome than viral load among people receiving antiretroviral therapy. In addition, CD4 cell count prior to treatment is crucial to response to treatment. That is, if a patient starts treatment with a CD4 cell count below 200 cells/mm³, they are more likely to experience deteriorating health than if they start treatment when the CD4 cell count is above 200 cells/mm³.

CD4 cell count and response to treatment

The link between baseline CD4 cell count and response to treatment - in terms of viral load and clinical status - is now well established.

Numerous studies have found that risk of disease progression is reduced among people who start antiretroviral therapy when their CD4 cell count is above 200 cells/mm³. However, current evidence indicates there is no clinical (health) benefit to starting treatment with a CD4 cell count above 350 cells/mm³. Individuals who start treatment with a CD4 cell count below 200 cells/mm³ are more likely to experience disease progression than people who start treatment earlier. The predictive value of CD4 cell counts prior to therapy is used as the basis for guidelines concerning when to start therapy. See Arguments for delaying treatment in Anti-HIV therapy: When to start treatment.