Impact of changing case definitions for coronavirus disease 2019 (COVID-19) hospitalization on pandemic metrics
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Published on: November 10, 2023
Claire N Shappell1,2, Michael Klompas1,3, Christina Chan1
1Department of Population Medicine, Harvard Medical School/Harvard Pilgrim Health Care Institute, Boston, Massachusetts.
Insights
Different definitions for coronavirus disease 2019 (COVID-19) hospitalizations significantly alter case counts and patient outcomes. New surveillance definitions are needed to accurately capture and differentiate primary, contributing, or incidental COVID-19 hospitalizations.
Area of Science:
- Infectious Diseases
- Epidemiology
- Health Services Research
Background:
- Accurate case definitions for coronavirus disease 2019 (COVID-19) hospitalizations are crucial for epidemiological surveillance and outcome assessment.
- Existing definitions vary in their criteria, potentially leading to inconsistencies in reported case counts and patient characteristics.
Purpose of the Study:
- To evaluate the impact of six common COVID-19 hospitalization case definitions on hospitalization counts and in-hospital mortality.
- To assess the ability of these definitions to distinguish between primary/contributing versus incidental COVID-19 hospitalizations.
Main Methods:
- Retrospective analysis of adult hospitalizations across five Massachusetts acute-care hospitals from March 2020 to March 2022.
- Application of six case definitions, including positive SARS-CoV-2 PCR assay, PCR with dexamethasone, remdesivir, hypoxemia, institutional flags, or ICD-10 codes.
- Review of 100 PCR-positive cases to determine definition accuracy for classifying hospitalization type.
Main Results:
- COVID-19 hospitalization counts varied significantly across definitions, ranging from 1.5% to 5.2% of total encounters.
- Definitions incorporating treatments (dexamethasone, remdesivir) or hypoxemia identified sicker patients with higher mortality rates compared to PCR alone.
- International Classification of Disease, Tenth Revision (ICD-10) codes showed high sensitivity but low specificity, while PCR plus dexamethasone had high specificity but low sensitivity.
Conclusions:
- Commonly used COVID-19 hospitalization definitions produce inconsistent case counts and outcomes.
- These definitions exhibit limitations in differentiating primary or contributing COVID-19 hospitalizations from incidental ones.
- There is a need for improved surveillance definitions to better capture and delineate COVID-19-associated hospitalizations.
Objective:
To examine the impact of commonly used case definitions for coronavirus disease 2019 (COVID-19) hospitalizations on case counts and outcomes.
Design, Patients, And Setting:
Retrospective analysis of all adults hospitalized between March 1, 2020, and March 1, 2022, at 5 Massachusetts acute-care hospitals.
Interventions:
We applied 6 commonly used definitions of COVID-19 hospitalization: positive severe acute respiratory coronavirus virus 2 (SARS-CoV-2) polymerase chain reaction (PCR) assay within 14 days of admission, PCR plus dexamethasone administration, PCR plus remdesivir, PCR plus hypoxemia, institutional COVID-19 flag, or COVID-19 International Classification of Disease, Tenth Revision (ICD-10) codes. Outcomes included case counts and in-hospital mortality. Overall, 100 PCR-positive cases were reviewed to determine each definition's accuracy for distinguishing primary or contributing versus incidental COVID-19 hospitalizations.
Results:
Of 306,387 hospital encounters, 15,436 (5.0%) met the PCR-based definition. COVID-19 hospitalization counts varied substantially between definitions: 4,628 (1.5% of all encounters) for PCR plus dexamethasone, 5,757 (1.9%) for PCR plus remdesivir, 11,801 (3.9%) for PCR plus hypoxemia, 15,673 (5.1%) for institutional flags, and 15,868 (5.2%) for ICD-10 codes. Definitions requiring dexamethasone, hypoxemia, or remdesivir selected sicker patients compared to PCR alone (mortality rates 12.2%, 10.7%, and 8.8% vs 8.3%, respectively). Definitions requiring PCR plus remdesivir or dexamethasone did not detect a reduction in in-hospital mortality associated with the SARS-CoV-2 Omicron variant. ICD-10 codes had the highest sensitivity (98.4%) but low specificity (39.5%) for distinguishing primary or contributing versus incidental COVID-19 hospitalizations. PCR plus dexamethasone had the highest specificity (92.1%) but low sensitivity (35.5%).
Conclusions:
Commonly used definitions for COVID-19 hospitalizations generate variable case counts and outcomes and differentiate poorly between primary or contributing versus incidental COVID-19 hospitalizations. Surveillance definitions that better capture and delineate COVID-19-associated hospitalizations are needed.
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