Fig 1.
Flow diagram of VACO Index cohort selection.
Flow diagram showing selection of VACO Index cohorts from 5,834,543 patients active in VA care as of January 1, 2020. All COVID-19 tests were performed in the VA. Patients with COVID-19 tests after July 18, 2020 did not have 30 days of follow-up and were excluded from the analysis.
Table 1.
Characteristics of patients in VACO Index development and validation cohorts.
Table 2.
VACO Index development cohort unadjusted associations with 30-day mortality (n = 3,681; 480 deaths).
Fig 2.
Forest plot of VACO Index 30-day mortality multivariable model.
Forest plot of odds ratios (OR) and 95% confidence intervals (CI) of VACO Index variables from multivariable logistic regression model derived from development cohort (n = 3,681). Abbreviations: MI or PVD = history of myocardial infarction or peripheral vascular disease.
Table 3.
Validation of VACO Index 30-day COVID-19 mortality estimates using area under the receiver operating characteristic curves.
Fig 3.
Calibration plots of VACO Index: Development, early validation, late validation, and combined validation cohorts.
Calibration plots of VACO Index predicted 30-day mortality risk versus observed patient mortality across the cohorts. Error bars show 95% confidence intervals and dashed lines indicate perfect agreement between predicted versus observed patient mortality. a. Development cohort: test positive between March 2 and April 15, 2020, n = 3,681, 480 deaths. b. Early validation cohort: test positive between April 16 and May 18, 2020, n = 2,151, 253 deaths. c. Late validation cohort: test positive between May 19 and July 18, 2020, n = 7,491, 403 deaths. d. Combined early and late validation cohorts: test positive between April 16 and July 18, 2020, n = 9,642, 656 deaths.
Fig 4.
Calibration plots of VACO Index: Combined cohort subgroups.
Calibration plots of VACO Index 30-day predicted mortality risk versus observed patient mortality. Error bars show 95% confidence intervals and dashed lines indicate perfect agreement between predicted versus observed patient mortality. Development cohort: test positive between March 2 and April 15, 2020, n = 3,681, 480 deaths. Combined early and late validation cohorts: test positive between April 16 and July 18, 2020, n = 9,642, 656 deaths. Subgroups: Men vs women; Black vs non-Black race; Northeast (NE) + West (W) regions vs Southeast (SE) + Midwest (MW) regions.
Fig 5.
Range of 30-day mortality predictions from age alone and VACO Index.
Bar graphs demonstrating the additional variation in mortality prediction provided by the VACO Index over age alone across age categories in the combined validation cohort (n = 9,642). The diamonds indicate predicted 30-day mortality within each age category when only age is used to generate the predicted value. The bars show the range of predicted 30-day mortality within the same age category provided by the VACO Index, where age is supplemented with sex and comorbidities.