People infected with HIV may have years of good health before developing AIDS. Once AIDS is diagnosed, combination anti-retroviral treatment (cART) is effective at slowing its progression. Patients and their doctors face a major decision about when to start cART, and experts around the world have offered a variety of opinions. A recent article in the medical literature reports a new analysis of data on how to make this decision.
The CD4 cell count and its change with time are the primary factors used to monitor progression of HIV infection. Uninfected people have CD4 counts in the range of 500 to 1,200 cells per microliter of blood. (A different reference reports 700 to 1,000.) All current guidelines recommend cART treatment for patients with CD4 counts of 350 or less. When the count drops to 200, the immune system is too weak to fight opportunistic infections and the patient is classified as having AIDS.
Between 350 and 500 CD4 cells per microliter is a transition zone, where different medical organizations have different guidelines. Patients generally have no symptoms of AIDS. The United States Department of Health and Human Services panel gives a moderate to strong recommendation to initiate cART to patients in this range. However, there are disadvantages to starting early. Anti-retroviral drugs have serious side effects, and it is a demanding job to follow the treatment regime. Most HIV strains develop drug resistance quickly, so current therapy programs use multiple drugs at once. It is very important to take all the pills exactly on schedule. Some drugs have to be taken with food to improve absorption, and others must be taken on an empty stomach. As with all drug treatment for infectious pathogens, if you don't take all the pills precisely as prescribed, you run the risk of killing off the weak germs and leaving the strong ones to grow faster.
The international AIDS charity AVERT offers more details on its web site (see references). “Treatment should only be started once the person is ready,” they recommend.
Many doctors have used the rate of decline of CD4 cells as a guideline for when to recommend starting treatment. The International AIDS Society-USA suggests starting cART when the CD4 count drops by 100 cells per microliter per year, regardless of what the actual count is. The European AIDS Clinical Society suggests starting cART with a CD4 decline of 50 cells per microliter per year, in the range of 350 to 500 cells per microliter.
However, recent results from the CASCADE study report that the rate of decline of CD4 cells is not correlated with the success of anti-retroviral treatment. Thus, the decision of when to start treatment remains a very personal one.
References:
Wolbers M et al, “Pretreatment CD4 cell slope and progression to AIDS or death in HIV-infected patients initiating antiretroviral therapy – The CASCADE collaboration: A collaboration of 23 cohort studies”, PLoS Medicine 2010 February; 7(2): e1000239.
More about when to start treatment:
http://www.avert.org/antiretroviral.htm
CD4 counts in normal and HIV-infected individuals:
http://aids.about.com/od/technicalquestions/f/cd4.htm
Linda Fugate is a scientist and writer in Austin, Texas. She has a Ph.D. in Physics and an M.S. in Macromolecular Science and Engineering. Her background includes academic and industrial research in materials science. She currently writes song lyrics and health articles.