MUC4 and kidney failure: Within the critically ill COVID-19 patient group, MUC1 mRNA expression significantly correlated with mortality and renal failure (Figure 7, A and B), MUC13 mRNA expression with the time between symptom onset and hospital admission (Figure 7, A and C), MUC4 mRNA expression with the duration of invasive ventilation (Figure 7, A and D), and MUC16 mRNA expression with the need for invasive ventilation (Figure 7, A and E).