An idealized conceptual system architecture for an interoperable city/state/region/nation-wide HIE-based PRO platform that can be used for various analytics including CER. Orange: Typical HIE data sources; Dark green: Population health data sources; Light green: PRO data repositories; Light gray/dashed border: sample systems; Arrows with middle circle: PRO messaging standardization required. For the sake of simplicity the diagram does not show existing relationships among non-HIE components (e.g., connection between lab systems and EHRs) and alternative access points for CER researchers (e.g., CER researcher accessing isolated EHR-PRO data directly). Abbreviations: EHR=Electronic Health Record, PRO=Patient Reported Outcome, HIE=Health Information Exchange, CAT=Computerized Adaptive Test