Delphi methodology in health research: how to do it?

Introduction: Delphi technique is widely used to develop consensus on group opinion. However, no strict guidelines exist and various methods are often employed. The aim of this article was to reflect on Delphi methodology and provide guidance useful to researchers in integrative medicine. Methods: Two parallel Delphi studies were undertaken to achieve consensus on how to treat phantom limb pain with acupuncture. Whilst completing these studies methodological issues relating to Delphi technique were identified which may be of use to other researchers. Results: Ten areas were identified;, use of the term 'expert', sample size and sample heterogeneity/homogeneity, iteration, structure of round one, optimal number of response categories, inclusion/exclusion of data in subsequent rounds, participant feedback, defining consensus, stability of response and agreement, attrition. Conclusions: Defining and using the term 'expert' is problematic. Three rounds are optimal. Round one data collection and analysis need structuring to avoid generation of unmanageable amounts of data. Subsequent rounds should consider using Likert Scales with four to seven categories, with even number of categories eliminating the problems associated with midpoints. To ensure rigour, data should not be excluded from round three. Participant feedback should include both central tendency and a measure of dispersion and be presented graphically. Consensus should be clearly defined and not confused with stability of response or agreement. Attrition can be minimised by ensuring participants are well informed and through a short time frame between rounds. It is intended that this guidance may help future researchers. (C) 2015 Elsevier GmbH. All rights reserved.