Eurosurv. A comparison of two registry-based systems for the surveillance of persons hospitalised with COVID-19 in Norway, February 2020 to May 2022

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• Robert Whittaker[SUP]1[/SUP] , Salla Toikkanen[SUP]1[/SUP] , Katharine Dean[SUP]1[/SUP] , Trude Marie Lyngstad[SUP]2[/SUP] , Eirik Alnes Buanes[SUP]3,4[/SUP] , Hilde Kløvstad[SUP]1[/SUP] , Trine Hessevik Paulsen[SUP]1[/SUP] , Elina Seppälä[SUP]1[/SUP]

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Background

The surveillance of persons hospitalised with COVID-19 has been essential to ensure timely and appropriate public health response. Ideally, surveillance systems should distinguish persons hospitalised with COVID-19 from those hospitalised due to COVID-19.

Aim

We compared data in two national electronic health registries in Norway to critically appraise and inform the further development of the surveillance of persons hospitalised with COVID-19.

Method

We included hospitalised COVID-19 patients registered in the Norwegian Patient Registry (NPR) or the Norwegian Pandemic Registry (NoPaR) with admission dates between 17 February 2020 and 1 May 2022. We linked patients, identified overlapping hospitalisation periods and described the overlap between the registries. We described the prevalence of International Classification of Diseases (ICD-10) diagnosis codes and their combinations by main cause of admission (clinically assessed as COVID-19 or other), age and time.

Results

In the study period, 19,486 admissions with laboratory-confirmed COVID-19 were registered in NoPaR and 21,035 with the corresponding ICD-10 code U07.1 in NPR. Up to late 2021, there was a 90–100% overlap between the registries, which thereafter decreased to < 75%. The prevalence of ICD-10 codes varied by reported main cause, age and time.

Conclusion

Changes in patient cohorts, virus characteristics and the management of COVID-19 patients from late 2021 impacted the registration of patients and coding practices in the registries. Using ICD-10 codes for the surveillance of persons hospitalised due to COVID-19 requires age- and time-specific definitions and ongoing validation to consider temporal changes in patient cohorts and virus characteristics.



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https://www.eurosurveillance.org/content/10.2807/1560-7917.ES.2023.28.33.2200888