Decisions About Treatment
Doctors weigh the potential harm of a treatment against its potential benefit before recommending a course of action. Sometimes the benefit of treatment is improvement of symptoms, for example, reduction of pain. Benefit may also be improvement in function, for example, being able to walk farther. At times, benefit is cure of a disease. At other times, a treatment reduces the future likelihood of undesirable events, such as complications of a disease. Then, the benefit is a decrease in the risk of the event that people want to avoid.
Risk is the likelihood that a harmful outcome will occur. For example, a doctor may consider recommending a drug to reduce the risk of a stroke. A controlled clinical trial might show that of 1,000 people given this particular drug, 20 have a stroke despite taking the drug. The study might also show that of 1,000 people who are not given the drug, 40 have a stroke. The results of the study could be expressed as showing that the drug cut the risk of stroke in half, because 20 is half of 40 (relative decrease in risk). However, the results could also be expressed as showing that only 20 people of 1,000 had their risk of a stroke eliminated, because the difference between 40 and 20 is 20 (absolute decrease in risk). Cutting the risk of stroke in half sounds impressive, but the doctor has to consider whether a treatment that benefits only 20 of every 1,000 people who take it is the right choice for the person being treated. In determining whether it is the right choice to use the drug, both the doctor and the person being treated may consider a variety of information, such as how likely the drug is to cause serious side effects.
Research studies provide information about how much a treatment reduces the risk of a harmful outcome on average. But average effects do not always tell the doctor how an individual person will respond to a treatment.
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