Early antiretroviral therapy: the role of cohorts

Cause-specific mortality among HIV-infected individuals, by CD4(+) cell count at HAART initiation, compared with HIV-uninfected individuals

OBJECTIVES

To compare the proportion, timing and hazards of non-AIDS death and AIDS death among men and women who initiated HAART at different CD4 cell counts to mortality risks of HIV-uninfected persons with similar risk factors.

DESIGN

Prospective cohort studies.

METHODS

We used parametric mixture models to compare proportions of AIDS and non-AIDS mortality and ages at death, and multivariable Cox models to compare cause-specific hazards of mortality, across levels of CD4 cell count at HAART initiation (≤200 cells/μl: 'late', 201-350 cells/μl: 'intermediate', >350 cells/μl: 'early') and with HIV-uninfected individuals from the Multicenter AIDS Cohort Study and the Women's Interagency HIV Study. We used multiple imputation methods to address lead-time bias in sensitivity analysis.

RESULTS

Earlier initiators were more likely to die of non-AIDS causes (early: 78%, intermediate: 74%, late: 49%), and at older ages (median years 72, 69, 66), relative to later initiators. Estimated median ages at non-AIDS death for each CD4 cell count category were lower than that estimated for the HIV-uninfected group (75 years). In multivariable analysis, non-AIDS death hazard ratios relative to early initiators were 2.15 for late initiators (P < 0.01) and 1.66 for intermediate initiators (P = 0.01); AIDS death hazard ratios were 3.26 for late initiators (P < 0.01) and 1.20 for intermediate initiators (P = 0.28). Strikingly, the adjusted hazards for non-AIDS death among HIV-uninfected individuals and early initiators were nearly identical (hazard ratio 1.01). Inferences were unchanged after adjustment for lead-time bias.

CONCLUSION

Results suggest the possibility of reducing the risk of non-AIDS mortality among HIV-infected individuals to approximate that faced by comparable HIV-uninfected individuals.

Timing of HAART initiation and clinical outcomes in human immunodeficiency virus type 1 seroconverters

BACKGROUND

To estimate the clinical benefit of highly active antiretroviral therapy (HAART) initiation vs deferral in a given month in patients with CD4 cell counts less than 800/μL.

METHODS

In this observational cohort study of human immunodeficiency virus type 1 seroconverters from CASCADE (Concerted Action on SeroConversion to AIDS and Death in Europe), we constructed monthly sequential nested subcohorts between January 1996 and May 2009, including all eligible HAART-naive, AIDS-free individuals with a CD4 cell count less than 800/μL. The primary outcome was time to AIDS or death in those who initiated HAART in the baseline month compared with those who did not, pooled across subcohorts and stratified by CD4 cell count. Using inverse probability-of-treatment weighted survival curves and Cox proportional hazards regression models, we estimated the absolute and relative effects of treatment with robust 95% confidence intervals (CIs).

RESULTS

Of 9455 patients with 52,268 person-years of follow-up, 812 (8.6%) developed AIDS and 544 (5.8%) died. In CD4 cell count strata of 200 to 349, 350 to 499, and 500 to 799/μL, HAART initiation was associated with adjusted hazard ratios (95% CIs) for AIDS/death of 0.59 (0.43-0.81), 0.75 (0.49-1.14), and 1.10 (0.67-1.79), respectively. In the analysis of all-cause mortality, HAART initiation was associated with adjusted hazard ratios (95% CIs) of 0.71 (0.44-1.15), 0.51 (0.33-0.80), and 1.02 (0.49-2.12), respectively. Numbers needed to treat (95% CIs) to prevent 1 AIDS event or death within 3 years were 21 (14-38) and 34 (20-115) in CD4 cell count strata of 200 to 349 and 350 to 499/μL, respectively.

CONCLUSION

Compared with deferring in a given month, HAART initiation at CD4 cell counts less than 500/μL (but not 500-799/μL) was associated with slower disease progression.

When should antiretroviral therapy be started in HIV-positive persons?

Recommendations for the initiation of combination antiretroviral therapy in HIV-positive individuals are largely based on data from observational studies. Whilst all guidelines recommend immediate treatment in individuals with a CD4 count of less than 350 cells/mm(3), guidelines vary in their recommendations for treatment at higher CD4 counts. Several large cohort studies have published findings that contribute to the debate, although conclusions vary and results from these studies may be subject to bias.