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An important step forward in clinical research was taken in the mid-20th century with the development of the controlled clinical trial. This sets out to compare two groups of patients, one of which has had some form of treatment that the other group has not. The testing of a new drug is a case in point: one group receives the drug. the her a product identical in appearance, but which is known to be inert—a so-called placebo. At the end of the trial, the results of which can be assessed in various ways, it can be determined whether or not the drug is effective and safe. By the same technique two treatments can be compared, for example a new drug against a more familiar one. Because individuals differ physiologically and psychologically, the allocation of patients between the two groups must be made in a random fashion; some method independent of human choice must be used so that such differences are distributed equally between the two groups.
In order to reduce bias and make the trial as objective as possible the double-blind technique is sometimes used. In this procedure, neither the doctor nor the patients know which of two treatments is being given. Despite such precautions the results of such trials can be prejudiced, so that rigorous statistical analysis is required. It is obvious that many ethical, not to say legal, considerations arise, and it is essential that all patients have given their informed consent to be included. Difficulties arise when patients are unconscious, mentally confused, or otherwise unable to give their informed consent. Children present a special difficulty because not all laws agree that parents can legally commit a child to an experimental procedure. Trials, and indeed all forms of clinical research that involve patients, must often be submitted to a committee set up locally to scrutinize each proposal.
Surgery. In drug research the essential steps are taken by the chemists who synthesize or isolate new drugs in the laboratory; clinicians play only a subsidiary part. In developing new surgical operations clinicians play a more important role, though laboratory scientists and others in the background may also contribute largely. Many new operations have been made possible by advances in anesthesia, and these in turn depend upon engineers who have devised machines and chemists who have produced new drugs. Other operations are made possible by new materials, such as the alloys and plastics that are used to make .artificial hip and knee joints.
Whenever practicable, new operations are tried on animals before they are tried on patients. This practice is particularly relevant to organ transplants. Surgeons themselves—not experimental physiologists—transplanted kidneys, livers, and hearts in animals before attempting these procedures on patients. Experiments on animals are of limited value, however, because animals do not suffer from all of the same maladies as do humans.
Many other developments in modem surgical treatment rest on a firm basis of experimentation, often first in animals but also in humans; among them are renal dialysis (the artificial kidney), arterial bypass operations, embryo implantation, and exchange transfusions. These treatments are but a few of the more dramatic of a large range of therapeutic measures that have not only provided patients with new therapies but also have led to the acquisition of new knowledge of how the body works. Among the research projects of the late 20th century is that of gene transplantation, which has the potential of providing cures for cancer and other diseases.
SCREENING PROCEDURES
Реферат опубликован: 11/11/2009