Analytic procedures for evaluating health care. Statistical control charts

The concern for quality of health care motivates evaluation programs designed to monitor the health care system, patient outcome, and provider expertise. An array of audit methods and instruments for evaluating professional and institutional performance has been developed. Although evaluation is viewed by many as the basis for accountability and improvement of health care, few are aware that most existing evaluation programs are really data-collecting systems. Very little if any, analysis of the data is done with the objective of optimizing the system. The "sampling with intervention" procedures often used to monitor the health care delivery system are primarily directed toward the individual patient while the system and provider continue to operate in the established mode. This article outlines analytic procedures for interpreting evaluation data generated by quality control and audit systems. Five common univariate statistical quality control charts are described.