[Integration of primary and secondary data in the Study of Health in Pomerania and description of clinical outcomes using stroke as an example].

Objective: This study describes (i) the procedure of obtaining patients' consent for secondary data usage, (ii) the complexity of integrating data from multiple sources, and (iii) the correspondence among patients' self-reports, physician reports, routine data, hospital discharge diagnosis, and cause-of-death coding regarding stroke.
Methods: Data from the first follow-up (N=3 186) of the population-based Study of Health in Pomerania (SHIP) were used. These data were combined with secondary data from the Greifswald University Hospital, the association of statutory health insurance physicians Mecklenburg-Western Pomerania, physician reports, and death certificates.
Results: Consent for using health-related information from all data sources in question was obtained from more than 90% of the SHIP participants. Follow-up data from at least one source were available for 2 747 (86%) participants. For 92 participants information about the occurrence of stroke was found in at least one data source. In 59 cases the event appeared in only one data source, in 24 cases the event was found in 2 sources, and for 9 participants 3 data sources reported on the event.
Conclusion: Participants of a population-based cohort are highly willing to give consent for using their health-related information from secondary data sources. Yet, data integration is challenging due to considerable differences in data type, structure and coverage.
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