COVID-19 patients had significantly lower levels of β2GPI concentrations than healthy donors (68.7[IQR:52.6-90.5] ug/ml vs. 106.8 [IQR:80.2-127.3]ug/ml, p <0.001) (Figure 3A), consistent with the previous report, whereas no significant difference was observed in β2GPI concentrations between healthy donors and COVID-19 thrombosis patients (data not shown). Here, APOH is linked to COVID-19.