What Is Comparative Effectiveness?

The economic stimulus package signed into law earlier this year included $1.1 billion for comparative effectiveness research, which is supposed to help control health costs. That’s a lot of money for…what? It controls health costs … how?

There are a variety of definitions of comparative effectiveness provided by different official government and health research organizations. I like the way it was described by Peter Almenoff (Assistant Deputy Under Secretary for Health for Quality and Safety, Department of Veterans Affairs) in the May 2009 issue of Forum, a publication of the Department of Veterans Affairs Health Services Research & Development Service. A comparative effectiveness study is one that provides

information on the comparative benefits and/or harms of two or more alternative choices for a given clinical condition, patient population, or health care system.

How does this differ from ordinary clinical studies? Most clinical trials measure efficacy or the benefit of treatment under ideal conditions. The effects of treatment or intervention are compared to a placebo. In contrast, comparative effectiveness is related to the idea of a pragmatic trial in which effectiveness is measured relative to routine clinical practice (see Roland and Torgorson, Understanding Controlled Trials: What are Pragmatic Trials BMJ 1998;316:285).

If you want to know if the new, expensive drug to treat blog addiction is better than the cheap, old generic then you want a clinical effectiveness study. If you just want to know if the new, expensive anti-blog addiction drug is efficacious then a standard clinical trial comparing it to placebo is sufficient.

Approaches to comparative effectiveness include randomized trials, the scientific gold standard, and also observational studies using existing medical records. The latter approach requires the use of advanced statistical techniques to remove the effects of self-selection by type of treatment. If the trial isn’t randomized (i.e. is observational) then it is likely that individuals selecting treatment A differ systematically from those selecting treatment B. Outcomes of A and B are confounded by the differences in the population selecting the two treatment modalities, unless one uses statistical techniques to control for selection bias.

There is a debate as to whether comparative effectiveness should include cost effectiveness. Knowing only that treatment A has better outcomes than B will not help control health costs. What if treatment A costs $1 million and treatment B costs $1,000. What if A is only slightly better than B. Maybe if treatment B is adopted by a health insurer or system than vastly more patients can receive it than if treatment A is adopted. Comparative effectiveness, therefore, is only one step toward controlling costs. But it is an important step. With so much money out there for comparative effectiveness research I am sure we’ll all be hearing a lot more about it.

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