Tests may include the following: Alpha-1 antitrypsin level to evaluate for alpha-1 antitrypsin deficiency if high-resolution CT shows lower lobe emphysema Rheumatoid factor, antinuclear antibody (ANA), and antineutrophil cytoplasmic antibody testing if an autoimmune disorder is being considered Serum immunoglobulins (IgG, IgA, IgM) and serum electrophoresis to diagnose common variable immunodeficiency Serum IgE and Aspergillus precipitins if patients have eosinophilia, to rule out allergic bronchopulmonary aspergillosis Measurement of specific antibody levels against the capsular polysaccharide of S pneumoniae to aid in the diagnosis of various immunodeficiencies Sweat chloride tests (a positive test should be confirmed with a repeat test) and CFTR gene mutation analysis to diagnose cystic fibrosis (including in adults > 40 years without an identifiable cause of bronchiectasis, especially those with upper lobe involvement, malabsorption, or male infertility) Patients who have laboratory evidence of immuodeficiency should be referred for to an immunology specialist for evaluation because test results are often challenging to interpret.