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The practice of medicine is an art, performed for the healing and reduction in suffering of individual patients. Doctors practice their art through skilled application of available medical knowledge. Before the scientific and technological advances made in the last century, medical knowledge belonged to a select few and was passed from teachers to students as if from parents to children (see the first point in the Hippocratic Oath) (1). Although much had been learned through careful observation of human anatomy and disease, empirical evidence on prognoses and treatment outcomes was limited. Rational treatment decisions could be made deductively or on the basis of accepted beliefs; however, the inability to obtain extensive empirical evidence left the value of many treatments unproven and poorly understood.
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Modern medical researchers have applied the scientific method and taken advantage of advances in information technology to produce an ever-expanding body of evidence useful in medical decision making. The scientific method (construction of a hypothesis, design of an experiment, analysis of the data, and communication of the results) and the ability to collect and analyze large amounts of data enable researchers to study the comparative effects of different therapeutic approaches. Opinions on the best treatment for a specific condition are often considered to be hypotheses and tested in clinical studies. Application of statistical methods to data from large populations of patients provides the ability to estimate the average response to treatment, along with the variation in response among patients, and statistical models can be used to identify factors associated with better or poorer response.
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The art of medicine has been greatly expanded through the use of evidence-based methods. Multidisciplinary teams design, implement, analyze, and interpret the clinical studies that collectively form the body of evidence. Modern scientific principles require study reports to be publicly available and subject to scrutiny, often leading to debate about the appropriate interpretation of the results. Assessment of the validity of study results requires consideration of important factors such as the method of data collection and cleaning, relevance of the study patients to those seen in actual practice, methods for minimization of bias, and even the motivation of the investigators. Views about the best treatment are routinely examined in light of shared evidence, which is used to develop guidelines to aid in medical decision making. Modern physicians must have the ability to understand and interpret evidence and to make appropriate changes in their practice in light of new findings.
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The clinical perspective, focusing on a single patient, is now balanced by the statistical perspective, which makes inferences from populations. It is important to keep in mind that response to a therapy can vary from one patient to the next, and the results from a single patient therefore do not necessarily generalize to an entire group. For the same reason, results from a population do not accurately predict what will happen to each patient in the population. The goal of ...