By contrast, COVID-19 patients showed higher HDL diameter (p = 0.02), lower ApoE concentrations (p = 0.01) and lower phospholipid transfer protein (PLTP) activity (p < 0.01) than non-COVID-19 patients, while the plasma levels of HDL cholesterol, apo A1 and cholesteryl ester transfer protein (CETP) activity were not significantly different (Fig. 1). Here, APOE is linked to COVID-19.