What does COVID-19 testing results really say? The real statistics concealed behind the accessible data

Accurate and comprehensive testing is crucial for practitioners to portray the pandemic. Without testing there is no data; yet, the exact number of infected people cannot be determined due to the lack of comprehensive testing. The number of seropositive for SARS-CoV-2 infection is obviously relative to the extent of testing. However, the true number of infections might be still far higher than the reported values. To compare the countries based on the number of seropositive for SARS-CoV-2 infection is misleading, as there may not be enough tests being carried out to properly monitor the outbreak. In this paper, we closely look through the COVID-19 testing results. Herein, we try to draw conclusions based on the reported data: first, the presence of a possible relationship between COVID-19 transition and patients' age will be assessed. Then, the COVID-19 case fatality rate (CFR) is compared with the age-demographic data for different countries. Based on the results, a method for estimating a lower bound (minimum) for the number of actual positive cases will be developed and validated. Results of this study have shown that CFR is a metric reflecting the spread of the virus, but is a factor of the extent of testing and does not necessarily show the real size of the outbreak. Moreover, no large difference in susceptibility by age has been found. The results suggest the similarity between the age distribution of COVID-19 and the population age-demographic is improving over the course of the pandemic. In addition, countries with lower CFRs have a more similar COVID-19 age distribution, which is a result of more comprehensive testing. Finally, a method for estimation of the real number of infected people based on the age distributions, reported CFRs, and the extent of testing will be developed and validated.

Automated summary

Accurate and comprehensive testing is crucial for practitioners to portray the pandemic. The number of seropositive for SARS-CoV-2 infection is obviously relative to the extent of testing, and the true number of infections might be still far higher than the reported values. The COVID-19 case fatality rate (CFR) reflects the spread of the virus, but is a factor of the extent of testing and does not necessarily show the real size of the outbreak. Additionally, the study suggests a similarity between the age distribution of COVID-19 and the population age-demographic is improving over the course of the pandemic, especially in countries with lower CFRs due to more comprehensive testing.