Page 55 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

BIOMARKERS TO IDENTIFY SPUTUM EOSINOPHILIA IN DIFFERENT ADULT ASTHMA PHENOTYPES
DISCUSSION
This study shows that the diagnos c accuracy of FeNO and blood eosinophils to detect sputum eosinophilia did not signi cantly di er between obese and non-obese, atopic and non-atopic, (ex-)smoking and never-smoking, and severe and mild-moderate asthma pa ents. Total IgE was less accurate in atopic and obese pa ents than in non-atopic and non-obese pa ents. In unselected adult-onset asthma pa ents the diagnos c accuracy of FeNO and blood eosinophils is superior to that of total IgE, whilst combining FeNO and blood eosinophils into one model improves the overall diagnos c accuracy. The results suggest that FeNO and blood eosinophils (but not total IgE) can be used to con rm or exclude sputum eosinophilia with high certainty in up to half of adult asthma pa ents irrespec ve of asthma phenotype.
The present study is the rst to compare the diagnos c accuracy of FeNO, blood eosinophils, total IgE and their combina ons between di erent adult asthma phenotypes. Previous studies have mainly inves gated the diagnos c accuracy of these biomarkers in general asthma popula ons. Our ndings in the total study group of asthma pa ents on FeNO, blood eosinophils and total IgE are in line with the results of these previous studies, which we recently summarized in a systema c review 26, in which we found a pooled AUC of 0.75 for FeNO, 0.78 for blood eosinophils and 0.65 for total IgE. Our ndings on FeNO and blood eosinophils are more promising than those of two other recent reports 10, 27 in which the authors concluded that FeNO and blood eosinophils lack su cient sensi vity or speci city to be useful as markers of sputum eosinophilia. In addi on, we developed a combina on model of FeNO and blood eosinophils, which increased the diagnos c accuracy signi cantly compared to the separate markers. Adding four clinical variables to the model further increased the AUC, although only to a very minimal extend. For clinical purposes the use of two variables is obviously more prac cal.
The diagnos c accuracy of FeNO and blood eosinophils in detec ng sputum eosinophilia was similar in the di erent asthma phenotypes. This may be surprising, since remarkable di erences in airway eosinophilia and its associated cytokines and markers have been described in speci c asthma subgroups, for example, between obese and non-obese asthma pa ents 28. One study showed more eosinophils in the airway submucosa than in the airway lumen of obese pa ents with asthma, and also higher levels of interleukin(IL)-5 in BAL uid 13. Apparently, only a subset of obese asthma pa ents with eosinophilic airway in amma on shows sputum eosinophilia. In our study, total IgE was rela vely more accurate to predict sputum eosinophilia in non-obese pa ents as compared to obese pa ents, but had lower diagnos c accuracy than the other two biomarkers. Discordance between di erent biomarkers for airway eosinophilia has been reported previously.17, 29 More interes ngly, discordance between various biomarkers to e ects of an -in ammatory therapy or ability to predict
53