New study confirms “trial effect” in HIV clinical trials

Pills A new study has confirmed the existence of a “trial effect” in clinical trials for treatment of HIV. Trial effect is an umbrella term for the benefit experienced by study participants simply by virtue of their participating in the trial. It includes the benefit of newer and more effective treatments, the way those treatments are delivered, increased care and follow-up, and the patient’s own behavior change as a result of being under observation.

Researchers compared HIV suppression among patients who began highly active antiretroviral therapy (HAART) in a clinical trial with patients who received HAART in routine clinical care in two different time periods, 1996-1999 and 2000-2006. They found clear evidence of a trial effect during the earlier period, but not during the later period. Researchers offer that improvements to antiretroviral therapy (fewer pills and fewer side effects), and the change in attitude to HIV, which has come to be seen by many as a chronic, but treatable infection, may be among the explanations for the lack of demonstrable trial effect in the later period.

This is the first study to clearly demonstrate a trial effect in HIV clinical trials, and this has important implications moving forward. Documentation of a clinical trial effect should be considered when interpreting the generalizability of clinical trial results. At the same time, the fact that no trial effect was observed in the current HAART period argues that the efficacy demonstrated in clinical trials is likely to predict the effectiveness of the therapy in broader treatment populations. Clinicians and public health officials may have increased confidence that treatment guidelines based on clinical trial data are relevant to routine clinical care.


Does HAART Efficacy Translate to Effectiveness? Evidence for a Trial Effect. PLoS ONE 6(7): e21824. doi:10.1371/journal.pone.0021824
Background: Patients who participate in clinical trials may experience better clinical outcomes than patients who initiate similar therapy within clinical care (trial effect), but no published studies have evaluated a trial effect in HIV clinical trials.
Methods: To examine a trial effect we compared virologic suppression (VS) among patients who initiated HAART in a clinical trial versus in routine clinical care. VS was defined as a plasma HIV RNA #400 copies/ml at six months after HAART initiation and was assessed within strata of early (1996–99) or current (2000–06) HAART periods. Risk ratios (RR) were estimated using binomial models.
Results: Of 738 persons initiating HAART, 30.6% were women, 61.7% were black, 30% initiated therapy in a clinical trial and 67% (n = 496) had an evaluable six month HIV RNA result. HAART regimens differed between the early and current periods (p,0.001); unboosted PI regimens (55.6%) were more common in the early and NNRTI regimens (46.4%) were more common in the current period. Overall, 78% (95%CI 74, 82%) of patients achieved VS and trial participants were 16% more likely to achieve VS (unadjusted RR 1.16, 95%CI 1.06, 1.27). Comparing trial to non-trial participants, VS differed by study period. In the early period, trial participants initiating HAART were significantly more likely to achieve VS than non-trial participants (adjusted RR 1.33; 95%CI 1.15, 1.54), but not in the current period (adjusted RR 0.98; 95%CI 0.87, 1.11).
Conclusions: A clear clinical trial effect on suppression of HIV replication was observed in the early HAART period but not in the current period.

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