B2M and COVID-19: We compared the first principal component of the cytokines, β2M, and neopterin between the groups of patients with COVID-19 as a single test of difference in immunomarkers and found a significant difference (0.98; 95% CI, 0.36-1,61; P = .003), which remained significant after adjustment for time of sampling (0.54; 95% CI, 0.03-1.05; P = .04).