Summation, Saliency, and Saturation (3S): a continuum for a practical approach to assessing sample adequacy and...

Saturation is a common criterion for determining qualitative sample size adequacy and analytic completeness. The dynamic and fast-paced implementation research environment poses unique challenges for investigators conducting qualitative studies that seek to reach saturation. Saturated studies require an iterative, often lengthy and labor-intensive process of data collection and analysis, which is frequently at odds with implementation science's focus on rapid turnaround times for translating knowledge into practice. Moreover, despite its common usage, uncertainty around saturation's meaning and application remains. To date, there has been no systematic attempt to understand how the concept of saturation is defined and deployed specifically in the context of qualitative implementation research, or guidance on how to adapt the saturation concept in response to field-specific needs.

A concept synthesis was conducted to establish baseline knowledge that would inform field-specific guidance for assessing sample adequacy and analytic completeness in qualitative implementation research. Three leading implementation science journals were searched. Eligible studies (a) described empirical research, (b) discussed the saturation concept in the context of qualitative methodology, and (c) mentioned saturation in the body of the manuscript. Articles were systematically read and coded to identify meaningful content and patterns of interpretation.

Of 207 studies identified, 158 met eligibility for full-text review, and 146 were included in the final analysis. Findings show cursory treatment of the saturation concept. Various saturation-related terms and definitions were identified, as were prevailing interview sample sizes and citation patterns. Studies rarely explained how analytic completeness was determined, and discussion of saturation leading to theory or concept generation was sparse. These findings informed development of the 3S Continuum as an alternative approach for assessing qualitative sample adequacy and analytic completeness.

In implementation research, saturation as an analytic benchmark is seldom explained and difficult to attain. We propose a practical approach for reconceptualizing saturation as part of a larger continuum for assessing sample adequacy and analytic completeness. We aim to help implementation researchers navigate decisions about qualitative sample adequacy and analytic completeness in pragmatic and transparent ways.