Absolute risk, relative risk, and number needed to treat
Information provided by drug companies might not tell the full story
Doctors deal with queries about the risks and benefits of drugs daily. Patients read articles in a magazine or newspaper and they ask their doctor for guidance. He or she is expected to know more about clinical evidence than a journalist.
The curriculum in medical school covers anatomy, physiology, and other basic science quite well, but the teaching of evidence based medicine and its principles can be lacking.1 Many medical students hope to learn more about these topics later in their training, perhaps during residency,2 but a considerable number do not feel confident when trying to evaluate medical literature.34
Doctors should be able to interpret medical literature and evaluate clinical trials. Simple concepts from epidemiologists can help to put risks and benefits into perspective for our patients. In this article, we have used percentages rather than decimal fractions—that is, 50% rather than 0.5. The sums will be different depending on