CTSL and COVID-19: We identified a subset of protein analytes that were significantly (p < 0.001) elevated in hospitalized COVID-19 patients (ADM, CTSL1, HGF, IL-27, IL-6, KIM1, MERTK, MMP-1, MMP-12, OPG, TNFRSF10A, and TRAIL-R2) (Figure 4) (medians, interquartile ranges, and p-values are shown in Supplemental Table S3).