Statistics V: Introduction to clinical trials and systematic reviews

Decisions regarding the care of patients must be made through the diligent, unambiguous, and thoughtful use of current best evidence. Evidence-based medicine is an exhortation to integrate individual clinical proficiency with the best available evidence from systematic research. The benefit and harm to patients are quantified using mathematical estimates derived from research on population samples. This mathematically quantified evidence base is then used to inform clinical decision-making in individual patients. A recurring word in the definitions of evidence-based medicine is ‘research’ which may be defined as a systematic investigation which aims to increase the sum of knowledge. Research usually involves an attempt to test a hypothesis and may involve experiments on human subjects. Strict selection criteria are applied to patients entered into the research study which may involve the evaluation of a completely new treatment. Research should not to be confused with clinical audit which, according to a definition endorsed by the National Institute for Health and Clinical Excellence (NICE), is a quality improvement process that seeks to improve patient care and outcomes through systematic review of care against explicit criteria and the implementation of change. Aspects of the structure, processes, and outcomes of care are selected and systematically evaluated against explicit criteria. Where indicated, changes are implemented at an individual, team, or service level and further monitoring is used to confirm improvement in healthcare delivery.