Findings
D-PPAC (daily tool) and C-PPAC (weekly tool) are hybrid tools combining subjective patient inputs with objective activity monitor outputs, offering comprehensive insights into PA levels.
Psychometric validation indicates reliability, with high internal consistency and construct validity, though test-retest reliability is limited to specific trials.
Both tools are sensitive to changes in physical activity, but interpretation is limited in patients with very severe COPD or significant comorbidities.
Minimal important difference (MID) thresholds were identified for domains and total scores, though their clinical meaningfulness remains under investigation.
The tools’ interchangeability within trials is limited due to differing score ranges and measurement approaches.

Recommendations
Apply D-PPAC in trials where daily monitoring of physical activity is a primary endpoint.
Use C-PPAC in trials requiring supportive outcome data or when minimizing patient burden is critical.
Train investigators and patients thoroughly to ensure high compliance with both tools.
Further refine the total score derivation methodology to enhance interpretability and clinical relevance.
Expand validation efforts to include patients with broader comorbidity profiles and greater PA limitations.

Regulatory Considerations
Restrict the tools’ use to the validated activity monitors (Actigraph G3TX and Dynaport MoveMonitor) until further assessments are conducted.
MID thresholds should be used with caution, considering their limited precision and potential variability across different populations.
The use of these PRO tools in regulatory submissions must align with EMA’s guidance for COPD, ensuring endpoints align with study objectives.