If animal experiments correctly mimicked human disease and gave an accurate impression of our response to drugs, there would never be any need for studies with patients or clinical trials. But with most animal models of human illness either poor or non-existent,(1) it is not surprising that key advances in the understanding and treatment of disease often come not by experimenting on animals but from direct studies of people.
Human studies can take a variety of forms: while epidemiology requires an investigation of both sick and healthy groups of people, forming the basis of preventive health care, clinical observations are carried out on individual patients, often at the bedside. Doctors record case histories, measure blood pressure, take tissue and urine samples for analysis, and use modern scanning techniques such as positron emission tomography and magnetic resonance imaging to discover what is happening in the body. The resulting picture of disease provides a rational basis on which to devise treatments. Further vital information comes from autopsy findings and studies with healthy volunteers. Medical science also has a rich and productive history of researchers carrying out experiments on themselves.
The importance of human studies is stressed by Dr Paul Beeson of the Veterans Administration Medical Center in Seattle, who writes,(2) "progress by the study of man is by no means unusual, it is more nearly the rule, "Clinical researchers like Beeson argue that advances in the understanding and treatment of human disease must at least begin, and end, with studies of people.(3) To begin with, clinical observations are necessary to characterize the disease so that even if animal experiments are contemplated, scientists know which symptoms have to be induced. And ultimately, any findings that arise from animal research must be confirmed or rejected in human trials. Because the development of an animal model requires prior knowledge of the human condition, it is very difficult for such animal experiments to generate major insights.(5)
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