Sources of Evidence: Clinical Trials and Registries The notion of learning from observation of patients is as old as medicine itself. Over the last 50 years, our understanding of how best to turn raw observation into useful evidence has evolved considerably. Case reports, personal anecdotal experience, and small single-center case series are now recognized as having severe limitations to validity and have no role in formulating modern standards of practice. The major tools used to develop reliable evidence consist of the randomized clinical trial and the large observational registry. A registry or database is typically focused on a disease. | Chapter 003. Decision-Making in Clinical Medicine Part 10 Sources of Evidence Clinical Trials and Registries The notion of learning from observation of patients is as old as medicine itself. Over the last 50 years our understanding of how best to turn raw observation into useful evidence has evolved considerably. Case reports personal anecdotal experience and small single-center case series are now recognized as having severe limitations to validity and have no role in formulating modern standards of practice. The major tools used to develop reliable evidence consist of the randomized clinical trial and the large observational registry. A registry or database is typically focused on a disease or syndrome . cancer CAD heart failure a clinical procedure . bone marrow transplantation coronary revascularization or an administrative process . claims data used for billing and reimbursement . By definition in observational data the care of the patient is not controlled by the investigator. Carefully collected prospective observational data can achieve a level of quality approaching that of major clinical trial data. At the other end of the spectrum data collected retrospectively . chart review are limited in form and content to what previous observers thought was important to record which may not serve the research question under study particularly well. Data not specifically collected for research . claims data will often have important limitations that cannot be overcome in the analysis phase of the research. Advantages to observational data include the ability to capture a broader population than is typically represented in clinical trials. In addition observational data are the primary source of evidence for questions where a randomized trial cannot or will not be performed. For example it may be difficult to randomize patients to test diagnostic or therapeutic strategies that are unproven but widely accepted in practice. In addition we cannot randomize
