Methods for categorizing and treating subjects at risk for pulmonary exacerbation and disease progression

A method of determining pulmonary disease progression severity in a subject having cystic fibrosis and treating the subject, wherein the subject has experienced a pulmonary exacerbation, the method comprising:

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