Advantages
RCTs are considered by most to be the most reliable form of scientific evidence in the hierarchy of evidence that influences healthcare policy and practice because RCTs reduce spurious causality and bias. Results of RCTs may be combined in systematic reviews which are increasingly being used in the conduct of evidence-based medicine. Some examples of scientific organizations' considering RCTs or systematic reviews of RCTs to be the highest-quality evidence available are:
- As of 1998, the National Health and Medical Research Council of Australia designated "Level I" evidence as that "obtained from a systematic review of all relevant randomised controlled trials" and "Level II" evidence as that "obtained from at least one properly designed randomised controlled trial."
- Since at least 2001, in making clinical practice guideline recommendations the United States Preventive Services Task Force has considered both a study's design and its internal validity as indicators of its quality. It has recognized "evidence obtained from at least one properly randomized controlled trial" with good internal validity (i.e., a rating of "I-good") as the highest quality evidence available to it.
- The GRADE Working Group concluded in 2008 that "randomised trials without important limitations constitute high quality evidence."
- For issues involving "Therapy/Prevention, Aetiology/Harm", the Oxford Centre for Evidence-based Medicine as of 2011 defined "Level 1a" evidence as a systematic review of RCTs that are consistent with each other, and "Level 1b" evidence as an "individual RCT (with narrow Confidence Interval)."
Notable RCTs with unexpected results that contributed to changes in clinical practice include:
- After Food and Drug Administration approval, the antiarrhythmic agents flecainide and encainide came to market in 1986 and 1987 respectively. The non-randomized studies concerning the drugs were characterized as "glowing", and their sales increased to a combined total of approximately 165,000 prescriptions per month in early 1989. In that year, however, a preliminary report of a RCT concluded that the two drugs increased mortality. Sales of the drugs then decreased.
- Prior to 2002, based on observational studies, it was routine for physicians to prescribe hormone replacement therapy for post-menopausal women to prevent myocardial infarction. In 2002 and 2004, however, published RCTs from the Women's Health Initiative claimed that women taking hormone replacement therapy with estrogen plus progestin had a higher rate of myocardial infarctions than women on a placebo, and that estrogen-only hormone replacement therapy caused no reduction in the incidence of coronary heart disease. Possible explanations for the discrepancy between the observational studies and the RCTs involved differences in methodology, in the hormone regimens used, and in the populations studied. The use of hormone replacement therapy decreased after publication of the RCTs.
Read more about this topic: Randomized Controlled Trial
Famous quotes containing the word advantages:
“In 1845 he built himself a small framed house on the shores of Walden Pond, and lived there two years alone, a life of labor and study. This action was quite native and fit for him. No one who knew him would tax him with affectation. He was more unlike his neighbors in his thought than in his action. As soon as he had exhausted himself that advantages of his solitude, he abandoned it.”
—Ralph Waldo Emerson (1803–1882)
“[T]here is no Part of the World where Servants have those Privileges and Advantages as in England: They have no where else such plentiful Diet, large Wages, or indulgent Liberty: There is no place wherein they labour less, and yet where they are so little respectful, more wasteful, more negligent, or where they so frequently change their Masters.”
—Richard Steele (1672–1729)
“To say that a man is your Friend, means commonly no more than this, that he is not your enemy. Most contemplate only what would be the accidental and trifling advantages of Friendship, as that the Friend can assist in time of need by his substance, or his influence, or his counsel.... Even the utmost goodwill and harmony and practical kindness are not sufficient for Friendship, for Friends do not live in harmony merely, as some say, but in melody.”
—Henry David Thoreau (1817–1862)