Are HIV-infected patients with rapid CD4 cell decline a subgroup who benefit from early antiretroviral therapy?

We have developed a model to determine whether asymptomatic HIV-infected individuals who have a rapid CD4 cell decline are a subgroup who might benefit from early antiretroviral therapy. Data were obtained from a subgroup of participants in the Concorde and EACG020 trials, two randomized, double-blind, comparative trials of immediate (IMM) versus deferred (DEF) zidovudine therapy in asymptomatic HIV-infected individuals. The subgroup comprised 297 patients (IMM = 154, DEF = 143) who had at least one CD4 cell count before and after randomization. The median CD4 cell count at randomization was 491 x 10(6)/L, and the median follow-up was 61 months. The rate of CD4 decline before and after randomization was estimated using multi-level linear regression analysis, and patients were stratified into quartiles according to the rate of CD4 cell decline before randomization. Outcome measures were the development of AIDS, a 50% drop in CD4 count from the baseline, and death. A Cox proportional hazards model was used to examine whether the effect of zidovudine on disease progression varied according to the previous rate of CD4 decline. We found that a more rapid rate of CD4 decline before randomization was associated with a greater reduction in the rate of CD4 decline following IMM antiretroviral therapy (r = -0.5, P = 0.03). The greatest risk reduction in disease progression with IMM antiretroviral therapy was seen in the quartile of patients with the highest rate of CD4 decline (greater than or equal to 26 x 10(6) cells/L per 6 months) (hazards ratio (HR) = 0.61, 95% CI = 0.35-1.05). However, this effect was statistically significant in only the Concorde trial (HR = 0.48, 95% CI = 0.29-0.89). In contrast, we found no evidence in the EACG020 trial of any trend towards greater benefit in those with the most rapid CD4 cell decline. These findings suggest that asymptomatic patients with rapid CD4 cell decline are a subgroup likely to benefit from early antiretroviral therapy. This analytic approach should now be replicated in trials of combination therapy, and these should include viral load data.