A highly significant difference in age was found between the cohort of patients with heart failure (82.8 ± 10 years) and the other three cohorts (66.0 ± 16 years for COVID-19 samples, 63.2 ± 18 years for control samples and 67.8 ± 17 years for NCP samples, P < 0.001 for each comparison) and was not considered as a valid variable for further classification.
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