Progression to acquired immunodeficiency syndrome is influenced by CD4 T-lymphocyte count and time since seroconversion.

Progression to acquired immunodeficiency syndrome (AIDS) among persons infected with human immunodeficiency virus (HIV) varies considerably and may be influenced by factors such as age, smoking, number of male partners per year, and CD4 T-lymphocyte count. The loss of CD4 lymphocytes is known to be the dominant factor in the progression to AIDS. However, it is unclear whether the effect of the CD4 lymphocyte count is of such importance that persons with similar CD4 cell counts who have been infected for widely different lengths of time have the same risk of AIDS. While a CD4 count is easily obtainable, the precise amount of time since HIV infection is in most circumstances difficult to assess. In the present analysis, 259 Danish and 245 American homosexual men were followed for up to 14 years from 1981 to 1995. Two hundred and one persons seroconverted during the study period, and 112 had developed AIDS before the end of follow-up. CD4 lymphocyte count was highly correlated with the risk of developing AIDS (p < 0.001), but AIDS risk was not affected significantly by either age at infection, smoking, or number of male partners per year (p > 0.20 in all cases). Controlled for CD4 lymphocyte count, time since seroconversion was significant in explaining the risk of AIDS (p = 0.018), with a lower risk being seen during the first 3 years after seroconversion but no effect thereafter. These data confirm the central importance of CD4 lymphocyte level in the progression of HIV disease to AIDS, and suggest that rapid progression within 3 years of infection may be related to factors other than CD4 cell count.