The perception of the impact of Staffing and Study Design on Performance Outcomes in Clinical Trials

Background Protocol complexity in clinical trials has increased substantially, yet empirical evidence linking staffing configurations, complexity, and operational performance remains limited. This study examined how team composition and study design relate to perceived performance using a validated site-performance instrument and a standardized complexity classifier. Methods A cross-sectional study was conducted in a high-volume academic clinical trials unit (January–March 2025). For all actively recruiting or ongoing trials, contextual characteristics, protocol complexity (Ontario Protocol Assessment Level, OPAL), and staffing (Study Nurses, Study Coordinators, Data Managers) were recorded. Site performance was assessed using the Clinical Trial Site Performance Measure (CT-SPM), completed jointly by each trial team. Non-parametric tests and canonical discriminant analysis evaluated differences across phases and designs; univariate analyses of variance examined associations between staffing, complexity, and performance. Results A total of 362 trials were included, predominantly oncology (67.7%). Mean performance scores indicated overall good functioning. Participant retention and adverse event reporting differed across phases, with Phase I outperforming later phases. Study design showed larger effects: observational studies exceeded randomized controlled trials in retention, data quality, protocol compliance, and overall performance. Staffing demonstrated strong associations with performance: Study Nurses showed very large effects on retention (η²p=0.86) and substantial effects on data quality and compliance; Study Coordinators contributed moderate-to-large effects; Data Managers showed smaller, domain-specific contributions. OPAL-defined complexity did not explain additional variance once staffing was considered. Conclusions Perceived site performance is influenced more by staffing composition than by protocol complexity. Study Nurses and Study Coordinators—positioned at the clinical–operational interface—appear central in sustaining participant-facing and data-facing processes. Integrating standardized complexity assessments with structured performance measures may support a plan-and-prove approach to staffing and operational oversight.