Swedish Covid-19 Investigation for Future Insights - A Population Epidemiology Approach Using Register Linkage (SCIFI-PEARL)

Fredrik Nyberg; Stefan Franzén; Magnus Lindh; Lowie Vanfleteren; Niklas Hammar; Björn Wettermark; Johan Sundström; Ailiana Santosa; Staffan Björck; Magnus Gisslén

doi:10.2147/CLEP.S312742

Swedish Covid-19 Investigation for Future Insights - A Population Epidemiology Approach Using Register Linkage (SCIFI-PEARL)

Clin Epidemiol. 2021 Jul 30:13:649-659. doi: 10.2147/CLEP.S312742. eCollection 2021.

Authors

Fredrik Nyberg¹, Stefan Franzén^{1

2}, Magnus Lindh^{3

4}, Lowie Vanfleteren^{5

6}, Niklas Hammar⁷, Björn Wettermark⁸, Johan Sundström^{9

10}, Ailiana Santosa¹, Staffan Björck¹¹, Magnus Gisslén^{3

12}

Affiliations

¹ School of Public Health and Community Medicine, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
² National Diabetes Register, Centre of Registers Västra Götaland, Gothenburg, Sweden.
³ Department of Infectious Diseases, Institute of Biomedicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
⁴ Department of Clinical Microbiology, Sahlgrenska University Hospital, Gothenburg, Sweden.
⁵ COPD Center, Department of Respiratory Medicine and Allergology, Sahlgrenska University Hospital, Gothenburg, Sweden.
⁶ Department of Internal Medicine and Clinical Nutrition, Institute of Medicine, Sahlgrenska Academy, University of Gothenburg, Gothenburg, Sweden.
⁷ Unit of Epidemiology, Institute of Environmental Medicine, Karolinska Institute, Stockholm, Sweden.
⁸ Pharmacoepidemiology & Social Pharmacy, Department of Pharmacy, Uppsala University, Uppsala, Sweden.
⁹ Clinical Epidemiology Unit, Department of Medical Sciences, Uppsala University, Uppsala, Sweden.
¹⁰ The George Institute for Global Health, University of New South Wales, Sydney, Australia.
¹¹ Centre of Registers Västra Götaland, Gothenburg, Sweden.
¹² Region Västra Götaland, Department of Infectious Diseases, Sahlgrenska University Hospital, Gothenburg, Sweden.

Abstract

Background: In response to the Covid-19 pandemic, we designed and initiated a nationwide linked multi-register, regularly updated, observational study for timely response to urgent scientific questions.

Aim: To describe the SCIFI-PEARL (Swedish Covid-19 Investigation for Future Insights - a Population Epidemiology Approach using Register Linkage) linked database encompassing essentially all known diagnosed Swedish Covid-19 patients plus a large general population comparison cohort and outline its utility in the current and future phases of the pandemic.

Methods: Individuals with Covid-19 from the entire country are identified on a regularly updated basis, from different sources: all individuals from SmiNet, the national database of notifiable diseases, with positive SARS-CoV-2 polymerase chain reaction (PCR) test results; patients identified in the healthcare system by condition (ICD-10) or procedure codes in the National Patient Register or Cause-of-Death Register; patients identified through several disease-specific national quality registers (NQRs); and in two regions additionally patients identified in primary care. A comparison population was obtained by stratified random sampling from Swedish national population registers. Data from all these registers plus the National Prescribed Drug Register, the Cancer Register, national sociodemographic registers, some additional NQRs, the National Vaccination Register, and further data sources, are then linked to all study subjects (Covid-19 cases and population cohort). New cases in the study population and all data for all subjects are updated every few months, as required.

Conclusion and utility: The SCIFI-PEARL study cohort captures Swedish residents with Covid-19 on an ongoing basis, includes a representative general population comparison cohort, and links to a broad range of national and regional healthcare data for a comprehensive longitudinal view of the Covid-19 pandemic. By combining high-quality national registers with short time delay and continuous repeated linkage and updating, the project brings timely and internationally relevant data for epidemiological research on SARS-CoV-2. Our efforts provide an example and important learnings for similar efforts internationally in the future.

Keywords: SARS-CoV-2; data updates; longitudinal; observational research; population cohort.

Grants and funding

The core study is currently financed by grants from the Swedish state under the agreement between the Swedish government and the county councils, the ALF-agreement (Avtal om Läkarutbildning och Forskning/Medical Training and Research Agreement) grant ALFGBG-938453 and from FORMAS (Forskningsrådet för miljö, areella näringar och samhällsbyggande/Research Council for Environment, Agricultural Sciences and Spatial Planning), a government research council for sustainable development, grant 2020-02828. Additional grants supporting different aspects of ongoing research within the study include: the Swedish Heart Lung Foundation (20210030), Knut och Alice Wallenbergs Stiftelse/SciLifeLab (KAW 2021.0010), the Swedish Research Council (2021-05045, 2021-05450), and the Swedish Social Insurance Agency (FK 2021/011186).