SP-A serum levels appear to be significantly higher in patients with IPF than in patients with non-IPF ILDs, pulmonary infection, and healthy controls, while no differences are found in SP-D serum levels in IPF versus non-IPF ILD patients, although higher than those in pulmonary infection and healthy controls [50]. This evidence concerns the gene SFTPA2 and idiopathic pulmonary fibrosis.