What blood tests are used help determine the severity of asthma ?

Allergy immune tests: Blood levels of eosinophils, Immunoglobulin E level, blood immunocap allergy testing, blood oxygen level, as well as exhaled nitric oxide reflect asthma severity and some causes. Alpha 1 anti trypsin levels may point to early emphysema especially in asthmatics who smoke. The gold standard test is spirometry or a full breathing test. Sometimes exercise testing and MCR challenge is used