Participation thresholds and recruitment milestones for HIV cure-related trials: a modified Delphi study

Background Human immunodeficiency virus (HIV) cure-related trials remain insufficiently representative of populations most affected by HIV. Whether participation thresholds and recruitment milestones should be used to improve representativeness remains unresolved. We examined stakeholder views on whether, when, and how these approaches should be used. Methods We conducted a focused analysis of the participation-threshold domain from a larger modified Delphi study conducted in the USA. The continuing panel comprised 56 community, scientific, clinical, industry, ethics, regulatory, and community-engagement stakeholders. Across four rounds, the domain progressed from an open-ended question to structured statements, reassessment after summarized feedback, and follow-up with hesitant respondents. We used framework analysis for Round 1 responses, descriptive analyses for Round 2 and Round 3 items, and thematic analysis for Round 4 responses. We examined levels of support and disagreement across rounds; the protocol did not specify a numerical cutoff for declaring consensus. Results Stakeholders generally supported participation thresholds and recruitment milestones as tools for representation and accountability, but support was conditional. In Round 2 ( n = 46), the most frequently selected statements emphasized representation and equity because findings otherwise have limited relevance (54.3%) and enforcement of recruitment or enrollment milestones (45.7%). Other selections indicated that threshold use should depend on trial aims and research phase (19.6%) or that site selection may be preferable for subgroup-focused interventions (17.4%). Participants could select up to three statements, so percentages were not mutually exclusive. In Round 3 ( n = 48), when asked whether thresholds should be used in all future HIV cure-related trials, 75.0% answered “yes,” 20.8% answered “maybe,” and 4.2% answered “no.” Regarding implementation, 62.5% favored immediate enforcement of recruitment milestones, whereas 31.3% favored future use after clearer policies were established. In Round 4, hesitant respondents emphasized local epidemiology, flexibility across sites, and avoiding recruitment delays. These findings demonstrate substantial but conditional support; because no numerical consensus cutoff was prespecified, we do not claim that formal consensus was achieved. Conclusions Stakeholders generally supported participation thresholds and recruitment milestones, but not as rigid universal requirements. They favored approaches responsive to study phase, scientific aims, local context, feasibility, and ethical implementation. Trial registration Not applicable.