The role of clinical epidemiology in medical practice.

Epidemiological research has been carried out traditionally in the field on non-clinical populations and has sought to reveal the aetiology of disease. But in the 1960's a possible role for epidemiology in the study of clinical practice emerged. A series of articles on scientific methodology and clinical medicine argued that much of the reasoning underpinning clinical practice might be expressed in numerical terms. This numerical expression would require the counting of diseases and events in groups of patients and would thus employ similar methods to traditional epidemiology where diseases are counted in populations. Although the term 'clinical epidemiology' was introduced as early as 1938, Sackett was instrumental in promoting the concept in 1969 as the 'application by a physician... of epidemiologic and biometric methods to the study of the diagnostic and therapeutic process in order to effect an improvement in health'. The management of individual patients involves the clinician in a multitude of decisions, concerned with making a diagnosis, ordering tests, prescribing treatment and estimating prognosis. Decisions are often made in a state of uncertainty because no reasonably objective information is available to indicate the best decision in the given circumstances, or because the most appropriate sequence of decisions for an individual patient is not apparent. Although the state of the art does not allow us to do this completely, the role of clinical epidemiology is, by way of clinical research, to provide clinicians with the information to make decisions that are most appropriate for the welfare of their patients, and in combination with information derived from decision theory to make these decisions rapidly and logically.(ABSTRACT TRUNCATED AT 250 WORDS)