Meaning

Comparative effectiveness is a neologism for comparing different medical interventions in terms of their clinical and/or economic effectiveness. It is still unclear whether the comparative effectiveness research funded by the American Recovery and Reinvestment Act (the "stimulus bill", which set more than more than $1 billion for comparative effectiveness research) will include also economic cost-effectiveness or just clinical cost-effectiveness.

Effectiveness and Difference to Efficacy

Effective care is often characterized as proven to work in the "real world". Whereas clinical trials in highly selected patient populations often without any significant co-morbidities are used for market approval (phase III trials), they only show that a drug or another treatment is efficacious. Often, these trials are only placebo-controlled to show that this particularly treatment works. Effectiveness goes two steps further: First, it entails typical users that the treatment is used for. And second, effectiveness often compares the effects of treatment to another treatment, not just the placebo effect.

Comparative Clinical Effectiveness

Most frequently clinical cost effectiveness can only be estimated from clinical studies, e.g. from randomized controlled trials. In recent years, more and more studies, in particularly publicly funded studies, have compared two or more treatments to each other. These studies are called "head-to-head" studies, and they are in contrast to placebo-controlled trials.

One goal of a placebo-controlled trial is just to show that a treatment is more efficacious than just the "placebo effect". This is not to say that a placebo does not work; to the contrary, a placebo usually has a well-documented effect on the symptoms of the patient. This placebo effect is poorly understood. Because placebos might affect the treatment differently if a patients knows if he or she is taking the placebo or the "verum", i.e., the real drug, the trial should be blinded. Since the patients might deduce - maybe just sub-consciously - that they are subject to placebo or verum treatment, placebo-controls need to be double-blind with adequate allocation concealment.

Comparative clinical effectiveness uses head-to-head studies to compare two or more different treatments. A good way is to evaluate a new treatment is to compare it to the current best treatment. In experimental studies such as randomized controlled trials, this can be estimated from the efficacy. Whenever possible, data from true clinical settings should be analysed and compared to these efficacy data.

If there are no head-to-head studies available, meta-analysis can quantitatively synthesize the results of both the placebo-controlled studies of the old and the new treatment. New techniques, nicknamed network meta-analysis, may enable the indirect comparison of two or more treatments if they have one treatment in common. However, these techniques should be used with caution as they might lead to false conclusions if the heterogeneity among trials is not acceptably low enough.