Placebo of HIV Trials

A new study confirms that a “trial effect”—in which patients improve simply as a result of taking part in a drug study—once existed among HIV trial participants.

Jef Akst
Jul 14, 2011


Between 1996 and 1999, HIV patients treated with highly active antiretroviral therapy (HAART) as part of a clinical trial showed greater viral suppression than those patients who received the same treatment in a routine hospital setting, according to researchers at the University of North Carolina School of Medicine, demonstrating that just taking part in a clinical trial was enough to have a positive effect on health outcomes. The documentation of a so-called “trial effect,” which is assumed to be the result of increased care and follow-up as well as changes in the patients’ behavior, could impact how researchers design clinical trial and analyze the resulting data.

“Trial effect is notoriously difficult to test,” lead author Prema Menezes said in a press release. “This is the first study to clearly demonstrate a trial effect in HIV clinical trials, and this has important implications moving forward.”

The researchers found no evidence, however, of a similar effect in HIV patients treated with HAART in trials from 2000 to 2006. This difference may be due to an overall change in HIV perception, which has become a very treatable infection, and improvements in the therapy itself, the authors say. Regardless of the explanation, the lack of a trial effect in more recent HIV trials suggests that their results are probably an accurate representation of the treatment’s efficacy, even when administered in a non-trial setting.