How many subjects are enough for symptom-focused concept elicitation studies? A retrospective analysis of saturation across twenty-six studies

Abstract

A33ies, 432 symptom concepts (range 7-33, M= 16.6 [SD] 6.4) were elicited. Each sample was divided into quartiles based on the chronology of individual interviews. Study results (i.e., patient reports) were then reviewed to determine the interview number and quartile in which each concept was first elicited. Results: Analysis showed that 84.0% (n= 363), 92.4% (n= 399), 97.2% (n= 420), and 99.3% (n= 429) of all elicited concepts had emerged by the tenth, fifteenth, twentieth, and twenty-fifth interview, respectively. Less than 1% (n= 3) of concepts emerged after the 25thinterview in samples with > 25 subjects. ConClusions: While a variety of factors inform sample size decisions in concept elicitation interview studies, this analysis suggests that researchers can reasonably expect to elicit 95% to 100% of the targeted disease-related symptoms-level concepts, and thus achieve saturation, through the conduct of 20 to 25 interviews.

A Comprehensive Conceptual Model of the Experience of Chronic Itch in Adults

“…All patients in the semistructured patient interviews were recruited from a single quaternary care center, though patients resided in 4 different Midwestern states. The sample size of the concept elicitation interviews was consistent with previous qualitative research [17,18], and we achieved saturation at interview 31. Nevertheless, larger studies are underway to determine whether novel concepts in our model of itch are generalizable to all patients with itch.…”

“…when no new relevant concepts are elicited) rather than a formal power analysis. Sample size consideration was based on previous research suggesting that 6-12 interviews are typically required for theoretical saturation [16][17][18]. We worked within that range in selection of 8 experts, but chose to oversample patients (n=33) for semi-structured interviews, to ensure adequate representation of the range of etiologies and severities of pruritic dermatologic disorders, as well as uremic pruritus, generalized idiopathic pruritus and rheumatologic disease.…”

Development and Validation of the FSIQ-RMS: A New Patient-Reported Questionnaire to Assess Symptoms and Impacts of Fatigue in Relapsing Multiple Sclerosis

“…A sample size of 15 was anticipated to be sufficient to achieve saturation. 28 Two additional participants were recruited to account for no-shows or cancellations.…”

Development and content validity of new patient-reported outcome questionnaires to assess the signs and symptoms and impact of atopic dermatitis: the Atopic Dermatitis Symptom Scale (ADerm-SS) and the Atopic Dermatitis Impact Scale (ADerm-IS)

“…Confirmation of the concepts included in the draft PRO questionnaires and content evaluation of the ADerm-SS and ADerm-IS were assessed through hybrid CE and CD interviews with adult patients with moderate-to-severe AD (n ¼ 15). Sample size estimates were based on predictions about the number of patients needed to achieve saturation, which is the point at which no new relevant information is gained from additional interviews 7,17,18 .…”

“…The CE data were utilized to develop a patient-centered conceptual model ( Figure 2) 21 , and the sign-, symptom-, and impact-related concepts described by participants were analyzed and tabulated with regard to (1) the frequency of participant report, (2) the words used by participants to describe the concept, (3) the bothersomeness of the concept to participants, and (4) the importance participants attached to improvement in the concept as an outcome of effective treatment. Additionally, the CE data were analyzed in regard to saturation, providing evidence that the study sample was large enough that additional interviews were unlikely to produce new relevant and important concepts 7,17,18 .…”