Methodological options of the nominal group technique for survey item elicitation in health research: A scoping review

To conduct a scoping review that identifies different nominal group technique (NGT) methods used to elicit items for health surveys, and their advantages and disadvantages. We conducted a comprehensive search process from database inception to July 22, 2019 in Medline, EMBASE, PsychInfo, CINAHL, Cochrane Central and Scopus without language restriction. We screened titles and abstracts. Data from potentially relevant articles were extracted by one reviewer and verified by a second reviewer, with disagreements resolved by consensus or a third reviewer. We included 57 studies, which used between 1 and 41 nominal groups that included between 2 and 30 participants per group. We grouped the 30 identified decision points for the NGT process into two stages common to most qualitative group methods [Research objectives; Group characteristics] and three stages related to the nominal groups themselves [Eliciting survey items; Refining survey elicited items from stage 3; Evaluating and selecting final survey items]. We discuss the advantages and disadvantages of each option in relation to specific study contexts. Investigators should carefully consider their options for each of the identified decision points and document the reasons for their choices in their protocol to maximize validity and transparency.