Receiver operating curve (ROC) analysis showed that KL-6 concentrations, evaluated by Lumipuse G600II (Figure 2), distinguished severe from non-severe COVID-19 patients with an area under the curve (AUC) of 99.8% and the best cut-off value was 448 U/mL with 97.1% specificity and 100% sensitivity. Here, MUC1 is linked to COVID-19.