Endpoint Landscape

Digital endpoints and clinician-rated scales capture different dimensions of motor function. Traditional scales like TETRAS and MDS-UPDRS provide integrated clinical assessments that reflect functional impact and treatment experience. Digital kinematic analysis captures continuous biomechanical signals with high precision and reproducibility. Many modern trial designs use both: a traditional scale as the primary endpoint (given regulatory precedent) with digital endpoints as secondary or exploratory measures that improve sensitivity to treatment effects.

Intraclass correlation coefficient (ICC) measures the consistency of repeated measurements. Higher ICC means less measurement noise, which improves statistical power and reduces the number of subjects needed to detect a treatment effect. Automated digital extraction achieves ICC 0.97 because the same algorithm processes every assessment identically. Clinician-rated scales like TETRAS (ICC 0.74-0.85) involve trained human judgment, which is valuable for clinical interpretation but introduces variability that requires larger samples to accommodate.

Digital endpoints are not intended to replace traditional scales but to complement them. TETRAS and MDS-UPDRS have decades of regulatory precedent and normative data. Digital endpoints add value by providing objective, continuous, high-frequency measurements that can detect treatment effects earlier and with fewer subjects. The FDA has shown increasing openness to digital endpoints as secondary and co-primary measures. The most practical path forward is a combined endpoint strategy that preserves regulatory continuity while gaining the precision advantages of digital assessment.

21 CFR Part 11 is the FDA regulation governing electronic records and electronic signatures. Compliance requires audit trails, access controls, data integrity validation, and system validation documentation. Digital endpoint platforms designed for regulatory submission must meet these requirements. Traditional pen-and-paper rating scales are not electronic instruments, so this regulation does not apply to them directly, though their data is typically entered into compliant EDC systems.

A combined strategy pairs the regulatory precedent of traditional scales with the statistical power of digital endpoints. Traditional scales provide the clinical meaningfulness interpretive framework that regulators and clinicians expect. Digital endpoints reduce sample size requirements (potentially by 60-70% for some measures), enable remote data collection for decentralized trials, and generate objective longitudinal data that captures subtle treatment effects. This approach de-risks the trial by maintaining a validated primary endpoint while adding digital measures that strengthen the evidence package.