SAA1 and chronic obstructive pulmonary disease: Here, both comparisons of AC with or w/o COPD vs. COPD resulted in 11 significantly differentially abundant proteins of which, however, only three proteins were regulated in both comparisons (Sulfhydryl oxidase 1 (QSOX1), Serum amyloid A-1 protein (SAA1), and Ig kappa light chain (no gene name; Supplementary Tables S3 and S4)).