Unmeasured confounding caused slightly better response to HAART within than outside a randomized controlled trial

Abstract

Objective To compare the outcome of highly active antiretroviral therapy (HAART) in HIV-infected patients initiating equivalent regimens within and outside a randomized controlled trial (RCT). Study Design and Setting The Danish Protease Inhibitor Study (DAPIS) was a national multicenter RCT comparing initial treatment with indinavir, ritonavir, or saquinavir/ritonavir during 96 weeks. From the Danish HIV Cohort Study we identified all patients initiating one of these protease-inhibitor-based HAART regimens: 425 patients within DAPIS and 677 outside the trial. We compared viral load, CD4 count response, and mortality. Results At weeks 96 and 240, trial participants were more likely than nonparticipants to have undetectable viral load (adjusted odds ratio [adOR] 1.28 [95% CI = 0.94–1.74] and 1.70 [95% CI = 1.16–2.50]) and a CD4 increase ≥100 cells/μl (adOR 1.37 [95% CI = 1.03–1.82] and 1.53 [95% CI = 1.04–2.25]). For antiretroviral-experienced, but not for antiretroviral-naïve patients, trial participants had a lower risk of death (mortality rate ratio [MRR] = 0.46 [95% CI = 0.27–0.77]) than nonparticipants. This effect was moderated in adjusted analyses (MRR = 0.60 [0.33–1.07]). Conclusions Compared to nontrial patients, trial participants had better response to HAART. The differences were small defying the notion that results obtained in RCTs are unachievable in routine clinical practice.