CD8+ lymphocyte counts and the risk of death in advanced HIV infection

Mortality related to human immunodeficiency virus (HIV) infection occurs predominantly in patients with CD4+ lymphocyte counts of less than 50 cells/mm3. We followed 133 HIV-infected patients with enrollment CD4 counts of less than 50 cells/mm3 to determine if the risk of death during a 1-year period could be predicted by a single enrollment CD8+ lymphocyte count.

Enrollment data including age, sex, T-cell subset counts, p24 antigen status, antiretroviral use, and preexisting HIV-related illnesses were collected on a cohort of 133 consecutive patients with enrollment CD4 counts of less than 50 cells/mm3. The cohort was followed for 1 year, and survival data were analyzed in relation to enrollment variables.

The mean enrollment CD8 count of those patients alive at 1 year was 600 cells/mm3, compared with a mean enrollment CD8 count of only 370 cells/mm3 in patients who had died prior to 1 year (P < .001). For every 100-cell decline in the enrollment CD8 count, the risk of death increased by 16% (95% confidence interval [CI], 5% to 22%), independent of other enrollment variables, including CD4 counts and p24 antigen status. A significant CD8 count warning level of 415 cells/mm3, irrespective of the presence of other enrollment variables, was associated with death within 1 year. The Kaplan-Meier estimated chance of death within 1 year was 54% (95% CI, 42% to 66%) for patients with CD8 counts of less than 415 cells/mm3 compared with only 25% (95% CI, 14% to 36%) for patients with CD8 counts greater than 415 cells/mm3.

This study finds that a single CD8 count has important prognostic significance in patients with advanced HIV infection and suggests that potential therapies to enhance CD8 counts might be beneficial to patients with advanced HIV infection.