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(Circulation. 1998;97:707.)
© 1998 American Heart Association, Inc.

Correspondence

Measurement of Clinical Efficacy in Studies of Heart Failure

Thomas S. Rector, PhD

Senior Research Associate, Cardiovascular Division, University of Minnesota Medical School, Minneapolis, Minn

To the Editor:

A recent clinical investigation reported by Packer et al¹ used a multiplicity of end points to assess the efficacy of carvedilol for heart failure because the most appropriate measure(s) have not been firmly established. Statistically significant favorable effects of carvedilol compared with placebo were observed for measures commonly used in clinical practice, such as NYHA classification, physician's assessment of changes in clinical status, and asking patients if they felt better compared with baseline. These congruent results do not represent independent assessments. Other measures, including a previously validated quality-of-life questionnaire, did not demonstrate significant differences.^{2 3} These discrepant results may have been due to differences in the content of measures, timing of assessments, and statistical methods. Nevertheless, the authors concluded that these results have important implications for future clinical trials, implying that simple symptom assessments were adequate to assess clinical efficacy because they correspond with clinical practice and demonstrated differences compared with placebo. Are the simple symptom assessments adequate measures of therapeutic efficacy?

Reliable clinical measurements result from methods that can be applied consistently at different times and by different investigators.⁴ The NYHA classification has been shown to have poor interobserver agreement in part because asking about "ordinary" physical activities is rather imprecise.⁵ When standard activities such as walking a specific distance or climbing a flight of stairs are used, it can enhance this measure's reliability,⁵ but concerns about what investigators take into consideration persist. For example, 60% of the patients in the carvedilol study were classified as NYHA . . . [Full Text of this Article]

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