An ordinal severity scale for COVID-19 retrospective studies using Electronic Health Record data

Abstract

Objectives: Although the World Health Organization (WHO) Clinical Progression Scale for COVID-19 is useful in prospective clinical trials, it cannot be effectively used with retrospective Electronic Health Record (EHR) datasets. Modifying the existing WHO Clinical Progression Scale, we developed an ordinal severity scale (OS) and assessed its usefulness in the analyses of COVID-19 patient outcomes using retrospective EHR data.

Materials and methods: An OS was developed to assign COVID-19 disease severity using the Observational Medical Outcomes Partnership common data model within the National COVID Cohort Collaborative (N3C) data enclave. We then evaluated usefulness of the developed OS using heterogenous EHR data from January 2020 to October 2021 submitted to N3C by 63 healthcare organizations across the United States. Principal component analysis (PCA) was employed to characterize changes in disease severity among patients during the 28-day period following COVID-19 diagnosis.

Results: The data set used in this analysis consists of 2 880 456 patients. PCA of the day-to-day variation in OS levels over the totality of the 28-day period revealed contrasting patterns of variation in disease severity within the first and second 14 days and illustrated the importance of evaluation over the full 28-day period.

Discussion: An OS with well-defined, robust features, based on discrete EHR data elements, is useful for assessments of COVID-19 patient outcomes, providing insights on the progression of COVID-19 disease severity over time.

Conclusions: The OS provides a framework that can facilitate better understanding of the course of acute COVID-19, informing clinical decision-making and resource allocation.

Keywords: COVID-19 ordinal scale; Electronic Health Record; N3C; National COVID Cohort Collaborative.

Figure 1.

Ordinal scale for EHR use compared to WHO Clinical Progression Scale. HER: Electronic Health Record; WHO: World Health Organization.

Figure 2.

Distribution of OS for hospitalized patients over the 28 days after SARS-CoV-2 diagnosis. OS Level 1: Outpatient, OS Level 3: Hospitalized, OS Level 5: Oxygen support, OS Level 7: Mechanical ventilator, OS Level 9: Organ support, OS Level 11: Death.

Figure 3.

Heatmap (A) and ribbon chart (B) of the proportion of patients that transition OS scores by week. The first number following W (week) represents the week since diagnosis (ie, week 1, 2, etc.); the second number represents the sample at given OS. Each cell in heat map represents probability of a patient starting at OS on vertical axis transitioning to OS level on the horizontal assess. Ribbon charts show transitions right to left, and color coded based on outcome in latest week.

Figure 4.

Variation of the first 4 principal components by daily OS. PC1: Overall disease severity over 28 days, PC2: Contrasts days 1–12 compared to days 13–28, PC3: Contrasts week 1 compared to week 2, PC4: Rapid changes within day 1–12, OS: Ordinal scale.

Figure 5.

PC1 versus PC2 grouped by maximum OS. OS: Ordinal scale; PC: Principal component.

Figure 6.

PC1 versus PC2 grouped by final OS after 28-day period. OS: Ordinal scale; PC: Principal component.