Defining the Short-term Risk of AIDS According to Current CD4 Cell Count and Viral Load in Treatment-naive Patients and Those Treated in the Monotherapy Era

One key piece of information required when deciding whether to initiate antiretroviral therapy is the risk of AIDS before the next clinic visit. Information on the short-term (6-month) risk of AIDS according to the current viral load and CD4 cell count is lacking in untreated individuals and those treated in the zidovudine monotherapy era (i.e., pre-September 1995), especially in those with CD4 cell count > 200 × 10⁶ cells/l.

In the present study, the risk of AIDS was assessed in 3226 subjects with viral load and CD4 cell count known before initiation of antiretroviral therapy or during the zidovudine monotherapy era. These were from the CASCADE Collaboration in which data from 20 cohorts of individuals with known dates of seroconversion to HIV, based in clinics in Europe and Australia, have been combined.

During a total 5126.0 person-years of follow-up, 219 individuals developed AIDS.

In those with current CD4 cell count < 200 × 10⁶ cells/l, 6-month risks were 4.9, 12.7, 17.7 and 22.4% for viral load groups < 10 000, 10 000-29 999, 30 000- 99 999 and ≥ 100 000 copies/ml, respectively.

For CD4 cell counts 200-349 × 10⁶ cells/l risks were 0.5, 1.6, 3.2 and 4.7%, respectively, for the four viral load groups while the corresponding values for group with CD4 cell count ≥ 350 × 10⁶ cells/l were 0.2%, 0.5%, 0.9% and 2.2%, respectively.

Results were similar when analysis was restricted to those with no antiretroviral drug experience. Older people had a higher risk of AIDS for a given CD4 cell count and viral load than younger people.

Combined with consideration of other issues, these estimates should prove useful information when deciding whether to initiate antiretroviral therapy in HIV-infected individuals.

01/21/04