If HIV treatment guidelines were updated to recommend beginning treatment at 500 CD4 cells, then more than half of all people with HIV would need to initiate antiretroviral (ARV) treatment within two years of becoming infected. This startling finding was presented Monday, July 20, at the Fifth International AIDS Society (IAS) Conference on HIV Pathogenesis, Treatment and Prevention in Cape Town.

Due to a number of recent studies showing detrimental effects of uncontrolled HIV replication—even at fairly high CD4 cell counts—international HIV treatment guidelines may begin recommending that people start ARV therapy when their CD4 counts drop below 500. The current recommendation is to start treatment at 350. Researchers have long known that a substantial number of people with HIV have significant CD4 cell drops shortly after infection, but no studies have examined how many people would need to start HIV treatment soon after infection, and how quickly this would occur.

Sara Lodi, PhD, from the Medical Research Council Clinical Trials Unit in London, and her colleagues with the CASCADE cohort study looked at the time it took for 11,702 recently infected individuals to have their CD4 counts drop below 500. People have been followed in CASCADE since 1992. Lodi’s team looked at CD4 counts at 6, 12, 24 and 36 months after people first had a positive HIV antibody test. The proportions of people whose CD4 counts dropped below 500 were 8 percent at 6 months, 28 percent at 1 year, 57 percent at 2 years, and 70 percent at 3 years after seroconverstion.

Lodi and her colleagues also found that people’s CD4 cells dropped more quickly the older they were when they became infected. In addition, people infected before 1997 appeared to progress more slowly than people infected after 1997.

The authors state that this data can help policymakers and researchers determine what kind of health care resources will be needed if treatment guidelines change. This will be especially vital if universal HIV testing becomes more widespread, as a third or more of people who test positive in the United States and Western Europe currently wait to get tested until their CD4 counts have dropped below 200.