Methods for Categorizing and Treating Subjects at Risk for Pulmonary Exacerbation and Disease Progression

A method of treating a subject having cystic fibrosis and at risk for severe pulmonary exacerbation, the method comprising:

• a. detecting in a sample from the subject mRNA expression level of CD64;
• b. determining the subject's risk for severe pulmonary exacerbation by calculating a disease risk score of mild, moderate or severe pulmonary exacerbation based on the subject's mRNA expression level of CD64 from step (a), wherein the subject's calculated disease risk score correlates to a risk score for mild, moderate or severe pulmonary exacerbation;
• and
• c. treating the subject determined to be at risk for severe exacerbation with treatments effective for treating severe pulmonary exacerbations.