Findings
DMOs offer a novel method to monitor mobility performance in real-world conditions across multiple diseases, but no current gold standard exists for direct comparison.
A 24-month observational clinical study with disease-specific cohorts is considered a valid exploratory step for validating DMOs.
Disease-specific endpoints (e.g., EDSS for MS, FEV1 for COPD) are supported as anchors for evaluating DMOs’ predictive capacity and construct validity.
The Later-Life Function & Disability Instrument (LLFDI) requires additional validation for use as a disease-independent biomarker, especially in younger populations.
Validation of DMOs as surrogate endpoints is contingent upon demonstrating robust correlations with established clinical outcomes in each disease.

Recommendations
Continue using disease-specific endpoints (e.g., EDSS for MS, FEV1 for COPD) to validate DMOs within individual diseases.
Validate the LLFDI tool across diverse age groups and diseases to establish its utility as a disease-independent biomarker.
Explore combining multiple DMOs to enhance predictive capacity where applicable.
Focus on disease-specific biomarkers until sufficient evidence supports the use of DMOs as disease-independent endpoints.
Conduct randomized clinical trials as a follow-up to the observational study to evaluate DMOs’ responsiveness to therapeutic interventions.

Regulatory Considerations
Established endpoints must be used to validate DMOs for consideration as secondary endpoints in regulatory submissions.
Disease-specific validation should be prioritized over disease-independent validation until robust evidence supports the latter.
Provide standardized and regionally consistent criteria for endpoints such as care home admission (PFF) or fall frequency (PD).
Correlate DMOs with widely accepted clinical measures (e.g., FEV1 in COPD) to strengthen regulatory positioning.
Incorporate randomization in future studies to further validate DMOs as surrogate endpoints predictive of clinical outcomes.