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Comparative Study
. 2023 Aug;28(33):2200888.
doi: 10.2807/1560-7917.ES.2023.28.33.2200888.

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

Robert Whittaker  1 , Salla Toikkanen  1 , Katharine Dean  1 , Trude Marie Lyngstad  2 , Eirik Alnes Buanes  3   4 , Hilde Kløvstad  1 , Trine Hessevik Paulsen  1 , Elina Seppälä  1
Affiliations
Comparative Study

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

Robert Whittaker et al. Euro Surveill. 2023 Aug.

Abstract

BackgroundThe 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.AimWe 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.MethodWe 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.ResultsIn 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.ConclusionChanges 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.

Keywords: COVID-19; International Classification of Diseases; Norway; electronic health registry; hospitalisation; surveillance.

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Conflict of interest statement

Conflict of interest: None declared.

Figures

Figure 1
Figure 1
Weekly number of hospital admissions of patients with confirmed COVID-19 in the Norwegian Pandemic Registry (n = 19,486) and the Norwegian Patient Registry (n = 21,035), Norway, 17 February 2020–1 May 2022
Figure 2
Figure 2
Number of COVID-19 admissions in Norwegian Pandemic Registry and Norwegian Patient Registry and a 4-week moving average of the proportion of overlapping admissions between the registries, Norway, 17 February 2020–1 May 2022
Figure 3
Figure 3
Prevalence of international classification of diseases diagnosis codes and code combinations by clinically assessed main cause of admission, Norway, 17 February 2020–1 May 2022
Figure 4
Figure 4
Weekly number of hospital admissions with confirmed COVID-19 as main cause or different international classification of diseases diagnosis code combinations among COVID-19 patientsa, Norway, 17 February 2020–1 May 2022
See this image and copyright information in PMC

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