Medical Risk Classification For Severe COVID-19 Based On Chronic Medical Conditions: A Comparative Analysis
Authors: Westerhof Ilse , de Boer Annemarijn , Lupattelli Angela , Slurink Isabel , Boldea Otilia , Nordeng Hedvig Marie Egeland , Bosdriesz Jizzo R. , Pijpers Frank , Schim van der Loeff Maarten , Knol Mirjam , van de Wijgert Janneke , Bruijning Patricia , Rozhnova Ganna 
Published: September 2024

Background

The European Centre for Disease Prevention and Control (ECDC) provides listings of medical conditions conferring high- or moderate-risk for severe COVID-19. In addition, individual European countries developed their own risk classifications for severe COVID-19 to select individuals recommended for annual COVID-19 vaccination. We assessed the discordance between the European and respective national medical risk classifications in assigning children and adults to risk groups for developing severe COVID-19 in populations of the Netherlands and Norway.

Methods

This multi-country, healthcare data-linkage study covered 17.4 million inhabitants of the Netherlands and 5.6 million inhabitants of Norway by 1 January 2020. Medical conditions were defined based on ICD-10 hospital discharge codes in the European and Dutch classifications, and on ICD-10 and ICPC-2 primary care codes in the Norwegian classification. Subjects were classified as high-, moderate-, or low-risk. Discordance was calculated as the proportion of the population with a different risk status in the respective national compared to the European classification.

Findings

The overall discordance between European and national risk classification was 12.0% in the Dutch and 13.8% in the Norwegian population. The European classification assigns more individuals to high-risk (9.0% and 9.2% of the Dutch and Norwegian populations, respectively) than the national classifications (1.5% and 3.0%, respectively). National classifications define more individuals as moderate-risk (11.3% and 12.7%, respectively) than the European classification (1.0% and 1.3%, respectively). Classification discordances most frequently involved subjects with cardiovascular disease, lung disease, and diabetes mellitus.

Interpretation

The European classification defines a substantially larger percentage of the population as high-risk for severe COVID-19 than the national classifications. This may have implications for post-pandemic vaccination programs. Further research should assess to what extent the medical conditions responsible for the classification discordances determine the risk of developing severe COVID-19.

Funding

ZonMw, EU, FCT, Norwegian Research Council’s COVID-19 Emergency Call, iAPOGEE.

Research in context

Evidence before this study

We searched PubMed for English-language articles published from 1 January 2020 to 1 July 2024, using the search terms ((((“COVID-19“[Title] OR “SARS-CoV-2“[Title]) AND (“sever*“[Title] OR “hospital*“[Title] OR “death“[Title] OR “decease*“[Title]) AND (“chronic condition*“[Title/Abstract] OR “comorbidit*“[Title/Abstract]) AND (“guideline“[Title] OR “classification“[Title] OR “system“[Title]) AND 2020/01/01:2024/07/01[Date - Create]) NOT “clinical trial“[Publication Type]) NOT “case reports“[Publication Type]). This search identified 64 studies, but none of them assessed the impact of different medical risk classifications for severe COVID-19 or compared them across countries or to the European classification.

Added value of this study

To the best of our knowledge, this is the first study that compared the impact of European and national medical risk classifications for severe COVID-19 by assigning the populations of the Netherlands and Norway to medical risk groups using national healthcare registries. We demonstrated important discrepancies between the European and respective national schemes in classifying high- and moderate-risk individuals in both countries. The chronic conditions responsible for the classification discordances were lung disease, cardiovascular disease, neurological disorders, diabetes mellitus, cancer, and hypertension.

Implications of all the available evidence

Our comparative analysis suggests that the choice between the European and national classifications may have important consequences for public health interventions such as vaccination campaigns. The variability in risk assignment based on chronic medical conditions underscores the absence of an international uniform approach. More research is needed to determine the extent to which each chronic medical condition impacts COVID-19 severity in the post-pandemic period, facilitating the refinement of risk classifications and supporting targeted public health interventions.