A practical approach to evidence grading.
BACKGROUND: The Institute for Clinical Systems Improvement (ICSI) is a collaboration of 17 Minnesota medical groups. Among other activities, ICSI develops health care guidelines and technology assessment reports. To maintain focus on the underlying evidence, ICSI has developed an evidence and conclusion grading system for use by the practicing clinicians who write the documents and use them in making decisions about patient care. THE EVIDENCE GRADING SYSTEM IN DETAIL: The centerpiece of the evidence grading system is the conclusion grading worksheet, which calls for statement of a conclusion, summarization of research reports that support or dispute the conclusion, assignment of classes and quality markers to the research reports, and assignment of a grade to the conclusion. EXPERIENCE AND RESULTS: The system has been used in the writing of more than 40 guidelines and numerous technology assessment reports. An example of a worksheet from the congestive heart failure guideline is presented. The system has helped the drafting groups to attend to the evidence. The methods have proven to be well accepted by practicing physicians and to be practical, although staff expertise in epidemiology is needed to support the system. Grading of conclusions appears to be reliable, although this characteristic of the system has not been rigorously tested. The outputs are valued by users of the documents. DISCUSSION: Although some residual problems remain to be solved, the system appears to be successful in overcoming the complexity of some published systems for grading evidence while still yielding a defensible classification of conclusions based on the strength of the underlying evidence.