To the Editor.
—Drs Kritchevsky and Simmons1 presented a clear and informative review of the principles of continuous quality improvement in a recent issue of JAMA.For years, hospital quality assurance programs have invested significant monetary and human resources in studying variation in clinical systems. We have, however, been myopic and wasteful in the interpretation of these data. Our focus has been to identify the poor performers and command them to improve—often without providing the information to allow them to escape the lower end of the bell curve. Sometimes we condemn without knowing whether the problem is truly a systemic or an extrasystemic cause of poor quality.Continuous quality improvement provides an innovative approach to the study of the variation in clinical systems. First, by using defined statistical methods, systemic and extrasystemic causes of poor quality can be clearly separated, thereby providing the best direction for improving a particular