Conditional mortality risk can explain differences in COVID-19 case fatality ratios around the globe

Aguiar, M.; Stollenwerk, N.

Objectives With COVID-19 infections resulting in death according to a hierarchy of risks, with age and pre-existing health conditions enhancing disease severity, the objective of this study is to estimate the condition-specific Case Fatality Ratio (CFR) for different sub-populations in Italy. Study design The design of the study was to estimate the “pre-existing comorbidity”-conditional CFR to eventually explain the mortality risk variability reported around in different countries. Methods We use the available information on pre-existing health conditions identified for deceased patients "positive with SARS-CoV-2" in Italy. We i) estimated the total number of deaths for different pre-existing health conditions categories and ii) calculated a conditional CFR based upon the number of co-morbidities prior to SARS-CoV-2 infection. Results Our results show a 0.6% conditional CFR for a population with zero pre-existing pathology, increasing to 13.9% for a population diagnosed with one and more pre-existing health conditions. Conclusions Condition-specific mortality risks are important to be evaluated during the COVID-19 pandemic, with potential elements to explain the CFR variability around the globe. A careful postmortem examination of deceased cases to differentiate death “caused by COVID-19” from death "positive with SARS-CoV-2” is therefore urgently needed and will likely improve our understanding of the COVID-19 mortality risk and virus pathogenicity.