Institute:Office of National Coordinator (ONC) Workforce Training Curriculum
Component:The Culture of Health Care
Lecture:Phrasing the clinical question
Harm and prognosis
Slide content:Evidence and Its Limits Randomized controlled trial Ideal, but often cannot be done or would be unethical to do so Cohort study Prospective study without randomization Particularly useful when poor outcomes are rare and huge sample size would be requirede.g., upper gastrointestinal hemorrhage with NSAIDs Problematic when groups are dissimilare.g., people who take NSAIDS may be sicker than or otherwise different from those who do not 7
Slide notes:7 Although a randomized controlled trial would provide the best evidence for harm, it often cant be done, or it would be unethical to do so. Therefore, we have to use lesser forms of evidence. Another type of study is a cohort study. This is a prospective study, where we take a group of patients who get exposed to something, and we follow them forward in time, but we dont randomize them. Cohort studies can be useful when poor outcomes are pretty rare such that a huge sample size would be required. For example, upper gastrointestinal hemorrhage that occurs with nonsteroidal anti-inflammatory drugs, or NSAIDs [ en -sayds ], such as Motrin and naproxen [ nuh- prok -suhn ], turns out to be relatively rare. We see it in clinical practice because so many patients take these drugs, but the rate of bleeding from NSAIDs is actually relatively low. In fact, it is difficult to do a clinical trial to detect that. So, a cohort study can help us in a situation where these poor outcomes are rare. Of course, cohort studies are problematic when the groups arent similar. For example, if we follow a cohort of people and we compare those who take the NSAID and those who dont, they are obviously different people. Those who take the NSAID are more likely to have ongoing medical problems, particularly those who require these drugs, so we dont get that benefit of randomization.