Analysis and interpretation of treatment effects in subgroups of patients in randomized clinical trials

Article Abstract:

Over 125 years ago it was pointed out that the response of the ''average'' patient may not be the same as that of the patient being treated. Because not all patients are identical, large clinical trials of therapeutic effects of a drug or procedure divide the subjects into subgroups of patients who are similar in certain ways. Subgroup analysis should be used to identify sameness or large differences in the treatment effects among patients with different characteristics. Proper and improper subgroups, magnitude of effect and qualitative interaction are defined in this paper. In addition, the effect of sample size on the power, or the ability to detect a difference, is discussed, and an example from a major study is presented. The more questions that are asked of a set of data, the greater the likelihood of finding a significant difference when there is none; therefore, hypotheses should be stated a priori, or before the analysis is begun. If hypotheses are developed a posteriori, that is, derived from the data, the effect is similar to betting on a horse race after the horses have crossed the finish line. In this case, medical explanations are sometimes manufactured to fit outcomes that may have occurred by chance. Other statistical problems, such as the classification of missing data, are also discussed. For these reasons, the overall average result of a randomized clinical trial is a more reliable estimate of treatment effect in the subgroups than the observed effects in the subgroups. (Consumer Summary produced by Reliance Medical Information, Inc.)

Clinical trials

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Overview of randomized trials of angiotensin-converting enzyme inhibitors on mortality and morbidity in patients with heart failure

Article Abstract:

Angiotensin-converting enzyme (ACE) inhibitors lower the risk of mortality and hospitalization for patients with symptomatic congestive heart failure. Use of these inhibitors should begin early, especially with patients who have low ejection fractions. They have experienced the most benefit from the treatment. Of 3,870 patients in controlled trials, the ACE inhibitor group recorded 611 deaths, or 15.8%, and the control group recorded 709 deaths, or 21.9%. Inhibitors evaluated included enalapril maleate, captopril, ramipril, quinapril hydrochloride and lisinopril. Results were consistent among groups, regardless of age, sex and etiology. Deaths from progressive heart failure were significantly reduced, and there were fewer fatal and nonfatal heart attacks, strokes and pulmonary emboli.

Health aspects, Care and treatment, Congestive heart failure, Angiotensin converting enzyme

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Oral Anticoagulant Therapy in Patients With Coronary Artery Disease: A Meta-analysis

Article Abstract:

Oral anticoagulants can lower the risk of heart attack and stroke in patients with coronary artery disease but they also cause excessive bleeding. This was the conclusion of researchers who analyzed 31 clinical trials that evaluated the use of oral anticoagulants in patients with coronary artery disease. Anticoagulants are drugs that prevent the formation of blood clots. Low-dose oral anticoagulants were no more effective than aspirin. Moderate- to high-doses were more effective than aspirin, but still increased the risk of excessive bleeding.

Prevention, Drug therapy, Coronary heart disease, Heart attack, Stroke (Disease), Stroke, Anticoagulants (Medicine), Anticoagulants

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