Evaluating Shared Decision-Making in Treatment Selection for Dupuytren Contracture: A Mixed Methods Approach

Background Choosing a suitable sample size in qualitative research is an area of conceptual debate and practical uncertainty. That sample size principles, guidelines and tools have been developed to enable researchers to set, and justify the acceptability of, their sample size is an indication that the issue constitutes an important marker of the quality of qualitative research. Nevertheless, research shows that sample size sufficiency reporting is often poor, if not absent, across a range of disciplinary fields. Methods A systematic analysis of single-interview-per-participant designs within three health-related journals from the disciplines of psychology, sociology and medicine, over a 15-year period, was conducted to examine whether and how sample sizes were justified and how sample size was characterised and discussed by authors. Data pertinent to sample size were extracted and analysed using qualitative and quantitative analytic techniques. Results Our findings demonstrate that provision of sample size justifications in qualitative health research is limited; is not contingent on the number of interviews; and relates to the journal of publication. Defence of sample size was most frequently supported across all three journals with reference to the principle of saturation and to pragmatic considerations. Qualitative sample sizes were predominantly – and often without justification – characterised as insufficient (i.e., ‘small’) and discussed in the context of study limitations. Sample size insufficiency was seen to threaten the validity and generalizability of studies’ results, with the latter being frequently conceived in nomothetic terms. Conclusions We recommend, firstly, that qualitative health researchers be more transparent about evaluations of their sample size sufficiency, situating these within broader and more encompassing assessments of data adequacy. Secondly, we invite researchers critically to consider how saturation parameters found in prior methodological studies and sample size community norms might best inform, and apply to, their own project and encourage that data adequacy is best appraised with reference to features that are intrinsic to the study at hand. Finally, those reviewing papers have a vital role in supporting and encouraging transparent study-specific reporting. Electronic supplementary material The online version of this article (10.1186/s12874-018-0594-7) contains supplementary material, which is available to authorized users.

To develop and psychometrically test a brief patient-report instrument for measuring Shared Decision Making (SDM) in clinical encounters. We revised an existing instrument (Shared Decision Making Questionnaire; SDM-Q), including the generation of new items and changing the response format. A 9-item version (SDM-Q-9) was developed and tested in a German primary care sample of 2351 patients via face validity ratings, investigation of acceptance, as well as factor and reliability analysis. Findings were cross-validated in a randomly selected subsample. The SDM-Q-9 showed face validity and high acceptance. Factor analysis revealed a clearly one-dimensional nature of the underlying construct. Both item difficulties and discrimination indices proved to be appropriate. Internal consistency yielded a Cronbach's alpha of 0.938 in the test sample. The SDM-Q-9 is a reliable and well accepted instrument. Generalizability of the findings is limited by the elderly sample living in rural areas of Germany. While the current results are promising, further testing of criterion validity and administration in other populations is necessary. The SDM-Q-9 can be used in studies investigating the effectiveness of interventions aimed at the implementation of SDM and as a quality indicator in health services assessments. Copyright 2009 Elsevier Ireland Ltd. All rights reserved.