North Indians have lower CD4 cell counts than individuals from the west. Consequently, the use of US Centers for Disease Control (CDC) categories of HIV disease severity to guide treatment decisions could lead to patients from northern India starting anti-HIV therapy or prophylaxis unnecessarily early, according to a paper published in the July edition of the Journal of Infection.
The CDC has three levels of HIV disease severity (CDC A, B, C). Asymptomatic individuals are classified as being in the CDC A category, and are considered to be have a competent immune system if their CD4 cell count is above 500 cells/mm3. Patients with symptoms of HIV infection, but who have not progressed to AIDS, or with a CD4 cell count between 500 – 200 cells/mm3 are categorised as CDC category B. Those who have developed an AIDS-defining condition or who have a CD4 cell count below 200 cells/mm3 are classified as being in the CDC C category.
However, it is well known that CD4 cell count can naturally vary between different ethnic groups without influencing the risk of HIV disease progression. For example, a CD4 cell count above 220 cells/mm3 in ethnic Chinese individuals is comparable to a CD4 cell count of above 500 cells/mm3 in western patients.
A proper local understanding of CD4 cell count and its implication for disease progression is essential for the appropriate use of antiretroviral therapy and prophylaxis against opportunistic infections. Indian investigators therefore conducted a cross-sectional observational study involving 376 HIV-positive patients from north India and 40 HIV-negative controls to “develop a new and revised classification that fits best with the north Indian set up.”
Mean CD4 cell count amongst the HIV-negative controls was a little under 800 cells/mm3. This was significantly higher than the mean CD4 cell count of 320 cells/mm3 observed in the patients in CDC A (range 380 - 259 cells/mm3). Mean CD4 cell count for patients in the CDC B category was 220 cells/mm3 (ranger 250 – 191 cells/mm3). For individuals with an AIDS diagnosis, the mean CD4 cell count was 106 cells/mm3 (range 121 – 92 cells/mm3).
If larger studies confirm their findings, the investigators propose that, rather than using the CDC CD4 cell count classification, the following categories would correlate better with the risk of HIV disease progression in north Indian individuals:
- Category A: Above 280 cells/mm3.
- Category B: 280 – 120 cells/mm3.
- Category C: Below 120 cells/mm3.
The investigators note, “the question of when to start antiretroviral therapy or prophylaxis for opportunistic infections could be dealt in north Indian HIV-positive patients only when clear guidelines will be formed after a well planned prospective study. So it is of immense importance that appropriate CD4 cut-off value be formed for the many ethnic groups that make up the Indian population.”
Attili VSS et al. Validity of existing CD4 classifications in north Indians, in predicting immune status. J of Infection 51: 41 – 46, 2005.