Therefore, in addition to FeNO, other variables such as previous diagnosis, signs and symptoms, specific laboratory testing including immunoglobulin E (IgE), radioallergosorbent test (RAST), alpha-1 antitrypsin deficiency (AATD) genotype, spirometry, or response to therapies administered throughout their medical care was utilized to update their diagnosis. Here, IGHE is linked to alpha 1-antitrypsin deficiency.