GDF15 and chronic obstructive pulmonary disease: In addition to CRP, considered above, five analytes increased significantly during AE-COPD: soluble intracellular adhesion molecule (sICAM)-1, soluble vascular cell adhesion molecule (sVCAM)-1, IL-10, IL-15, and growth and differentiation factor 15 (GDF-15) (Fig. 5a-e).