OBJECTIVES: Qualitative in-trial interviews are a valuable method of understanding patient perspectives of treatment and disease-related experiences within a clinical trial. Despite their increasing use, best practice guidelines for their conduct and implementation, including strategies for recruitment and sampling, are not widely available. The current research aims to address a gap in the available literature and explore approaches to participant sampling for in-trial interviews.

METHODS: A targeted literature search was conducted to identify in-trial interview studies between 2012 and 2024. Publications were selected for inclusion if the interviews were conducted with participants and/or caregivers within trials evaluating a medical treatment or device (excluding behavioral-based interventions) and related to patient experiences in the trial. Information relevant to the sampling strategy was documented.

RESULTS: Seventeen publications were selected for full text review; publications reported on interviews in a Phase 2 or Phase 3 trial (n=16) or a longitudinal trial (n=1) across 11 different therapeutic areas. Four studies (23.5%) aimed to interview all trial participants, while the remaining 13 (76.5%) used a convenience sampling approach to interview a subset of trial participants that agreed to participate. Practical considerations and/or interview-specific enrollment criteria were considered in targeting a subset of trial participants. Additionally, 12 studies (70.6%) articulated sample size targets, with six (35.3%) providing justification for those targets, including to reach thematic saturation, precedence in prior research, or to ensure representation of treatment arms, geographic location, and/or demographic characteristics.

CONCLUSIONS: While the majority of published in-trial interview studies were categorized as using a convenience sampling strategy, some studies targeted all participants. This review also identified factors that inform approaches to sampling, though justification for targets was not provided in all studies. Thus, when determining a sampling approach for in-trial interviews, researchers should establish and justify recruitment targets in addition to considering interview study objectives.