Institute:Office of National Coordinator (ONC) Workforce Training Curriculum
Component:The Culture of Health Care
Unit:Evidence-Based Practice
Lecture:Phrasing the clinical question
Harm and prognosis
Slide content:Using EBM to Assess Questions about Harm or Etiology Question is not whether someone exposed to agent gets ill, but whether those with illness have higher rate or amount of exposure Ideally assessed by randomized controlled trial, but RCT may be impractical or unethical Next best evidence comes from observational studies, which have limitations 4
Slide notes:4 This lecture discusses the two remaining types of basic clinical questions: harm and prognosis. We first discuss the use of evidence-based medicine to assess questions about harm or etiology. What causes a disease? Diseases may be caused by things in the air or water, bacteria, chemicals, radiation from the sun, or they may be caused by things that we do, such as a medical intervention that has a complication. The primary issue with assessing harm or etiology [ ee -tee- ol -uh- jee ] is not whether someone who is exposed to some kind of agent gets ill but whether those who have that illness have had a higher rate or amount of exposure. For example, just because someone who uses a cell phone gets brain cancer does not necessarily mean that the cell phone causes brain cancer. In fact, lets look at an example. Suppose we think that a certain chemical causes cancer. The ideal way to assess harm is to do a randomized controlled trial, so the best thing to do would be to get a group of people together and randomize half of them to getting exposed to the chemical and half of them not getting exposed. But obviously, exposing people to a chemical that might cause cancer is unethical, so we cant do that. We need other kinds of study designs that enable us to detect whether something causes harm. We have to go down to the next best level of evidence, which is observational studies; however, we need to be careful in how we interpret observational studies to ensure that they answer our questions.