MCEMP1 and HLA-DRA transcript levels displayed high AUC values (Mean AUC = 0.865 [95% CI 0.75–1.00]) (Fig. 3a), with the receiver-operator characteristic curve (ROC) plots showing that the combination of MCEMP1 and HLA-DRA was consistently able to distinguish severe from mild COVID-19 patients across all datasets (Fig. 3b and c, Supplementary Table S3). Here, HLA-DRA is linked to COVID-19.