To track how well different countries and U.S. states are responding to the pandemic—and to make valid cross-country and cross-state comparisons of key outcomes—uniform measures are needed. The authors of this report evaluate the comparability of commonly used COVID-19-related measures and make recommendations for the use and development of measures that would allow for more standardized and valid comparisons.
- What was the status of COVID-19 measurement in terms of testing/case identification, hospitalizations, mortality, and excess mortality during the early stages of the pandemic (December 2019–May 2020)?
- How did such measurement vary among countries and across U.S. states?
- How can countries and U.S. states measure COVID-19 indicators in ways that allow for more valid comparisons?
To track how well different countries and U.S. states are responding to the pandemic—and to make valid cross-country and cross-state comparisons—uniform measures are needed for key indicators, such as case identification/testing, hospitalization, mortality, and excess mortality. The authors of this report examined measures used in the early stages of the pandemic (December 2019–May 2020) and found tremendous variability in how different countries and U.S. states measure and report on COVID-19 indicators. The authors make recommendations for the use and development of measures that would allow for more standardized and valid comparisons.
There is tremendous variability in how different countries and U.S. states measure and report on COVID-19 indicators
- In terms of testing, there have been large differences in the types of tests used, who is tested (for example, only very symptomatic patients versus anyone who may have been exposed to an infected person), lag time for reporting results, and whether such reporting is mandatory.
- In terms of hospitalization, there has been considerable variation in whether hospitalization counts include patients suspected of having COVID-19 or only those with a positive test; in whether localities report hospitalization raw counts or cumulative counts or rates (e.g., per 100,000 population); and in whether reporting of hospitalization counts or rates is mandatory.
- In terms of mortality, there has been variation in how rates are defined; in whether reported deaths include only those for which COVID-19 was the main cause versus also those in which it contributed to death; in training that physicians receive in reporting the cause of death on death certificates; in whether any post-mortem testing is conducted; and in whether out-of-hospital deaths are included. There is also variation in whether excess mortality is reported as a pandemic outcome.
All the COVID-19-related measures currently in use have limitations
Long-term care facilities and nursing homes are of particular concern
- This population is often older and frail with multiple comorbidities, and they are at higher risk for poor outcomes from COVID-19. Therefore, particular focus on tracking, testing and mortality among this population is important.
- Assess the root causes of the lag in states' reporting of mortality and other information to the federal government.
- Explore ways to facilitate more timely reporting of the number of COVID-19 tests conducted, test results, hospitalizations, and excess mortality.
- Develop national standards around testing criteria (i.e., who to test), data collection, and reporting.
- Make the test positivity rate a standard component of reporting COVID-19 testing; states should report the total number of tests conducted, as well as those that are positive.
- Prioritize reporting of COVID-19 hospitalization per 100,000 population for surveillance purposes.
- Increase post-mortem testing capabilities to capture undiagnosed COVID-19 cases.
- Encourage continuing medical education for practicing clinicians to improve documentation of cause of death for COVID-19 and future public health emergencies and require more education and training around death certification in medical schools and residency training programs.
- Use a measure of excess mortality—the excess number of deaths observed during the pandemic relative to the expected number based on historical data—to compare the effects of COVID-19 across countries and states.
- Encourage more systematic reporting of all measures separately for congregate living facilities (e.g., nursing homes, short-term nursing facilities).
- Encourage systematic reporting of multiple measures (e.g., testing positivity rate, hospitalizations per 100,000 population, and excess mortality) given the strengths and limitations of each individual measure.
- Explore the development of a composite COVID-19 index that includes a combination of testing, hospitalizations, and/or mortality and that leverages the strengths of each of the related datasets.