Case-Fatality Rate and COVID-19 Death Characteristics in Italy
- Onder G, Rezza G, Brusaferro S.
- Case-Fatality Rate and Characteristics of Patients Dying in Relation to COVID-19 in Italy. JAMA 2020;Mar 23:[Epub ahead of print].
The following are key points to remember from this Viewpoint article on the case-fatality rate and characteristics of patients dying in relation to COVID-19 in Italy:
- Case Fatality Rate (CFR) is the proportion of individuals diagnosed with a disease who die from that disease. It is not a fixed, constant number but depends on patient characteristics, health care system features, and cultural and socioeconomic factors, among others.
- The CFR for coronavirus disease 2019 (COVID-19) in Italy is among the highest in the world and was 7.2% as of March 17, 2020. By comparison, the CFR in China was 2.3% as of February 11, 2020. There are potentially several reasons for these differences.
- CFR for COVID-19 depends on age and is much higher among the elderly than in younger and middle-aged individuals. Compared to China, the population of Italy is older, with 23% over age 65 years. Mortality among all age strata under age 70 years was similar between Italy and China and only among those ≥70 years old were differences between the countries noted. Thus, age explains at least part of the difference in CFR between Italy and China.
- Definition of COVID-19 related deaths differ across countries. In Italy, any death in a patient with positive reverse transcriptase–polymerase chain reaction (RT-PCR) testing for SARS-CoV-2 is considered COVID-19 related. Nonetheless, many other contributors to these deaths likely exist with chart review of 355 fatal cases showing high prevalence of ischemic heart disease (30%), diabetes (36%), active cancer (20%), and other serious conditions. Thus, prevalence of underlying conditions and how they are weighed in relation to counting COVID-19 related deaths could contribute to the observed differences in CFR between Italy and China.
- Testing strategies are critical for defining the denominator for the CFR. If testing prioritizes severely ill individuals and undersamples those with mild cases or who are asymptomatic, the denominator is underestimated, and CFR is overestimated. This may have occurred, as testing in Italy resulted in 19.3% positive cases, suggesting a focus on high probability, sicker individuals.
Keywords: Coronavirus, COVID-19, Cultural Characteristics, Diabetes Mellitus, Fatal Outcome, Geriatrics, Heart Failure, Italy, Myocardial Ischemia, Neoplasms, Primary Prevention, SARS Virus, Socioeconomic Factors
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