Delphi as a method to establish consensus for diagnostic criteria.

BACKGROUND/OBJECTIVES: To achieve a consensus, among a panel of experts, on the best clinical criteria for the clinical diagnosis of carpal tunnel syndrome (CTS).

METHODS: Experts rated the diagnostic importance of items from the clinical history and physical examination for CTS. The ratings were expressed on a 10-cm visual analog scale. The average and standard deviation of the scores for each item were returned to the panelists. The panel members evaluated the items a second time with knowledge of the group responses from the first round. The scores were standardized to minimize scaling variations and, after the second round, the items were ranked in order of importance assigned by the group. Cronbach's alpha was used as a measure of homogeneity for the rankings. Increasing homogeneity was considered to be an indication of consensus among the panelists.

RESULTS: Cronbach's alpha increased from 0.86 after the first round to 0.91 after the second iteration. Panelists who were relative outliers on the first round demonstrated a much higher correlation with the entire group after the second round.

CONCLUSIONS: Delphi is an effective method of establishing consensus for certain clinical questions. Cronbach's alpha was a useful statistic for measuring the extent of consensus among the panel members. Delphi was chosen from the possible methods of group process because of its inherent feasibility. The absence of a need by the panelists to meet in person removed any constraint on the geographic location of the panel members. In addition, the anonymous nature of Delphi was thought to be a key factor in avoiding a result that might be skewed by one or more persuasive panelists. Both of these characteristics were felt to be particularly important to the topic on which consensus was sought, the clinical diagnostic criteria for CTS. This movement in the opinions of some of the panelists appeared to result from the feedback of information describing the group opinion.