Page 57 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

BIOMARKERS TO IDENTIFY SPUTUM EOSINOPHILIA IN DIFFERENT ADULT ASTHMA PHENOTYPES
The major strength of our study is the large number and the extensive characteriza on of the pa ents, which enabled us to inves gate clinical (sub)phenotypes of adult-onset asthma. Another strength is that we reported biomarker thresholds at either high sensi vity or high speci city. These cut-o points are more useful for prac cing physicians to con rm or exclude airway eosinophilia with high certainty. A limita on of this approach, however, is that this method only gives a clear outcome in up to half of the pa ents; the remainder of the pa ents s ll needs to undergo sputum induc on to con rm or exclude sputum eosinophilia. Another possible limita on of our study is the number of missing sputum samples, in par cular in pa ents with mild-moderate asthma. This limits the extrapola on of our results to all pa ents with adult asthma. However, unsuccessful sputum induc on in mild-moderate asthma might be indica ve of a low level of sputum eosinophils, which ts in with the observed lower level of blood eosinophils in this group.
Our study has clinical implica ons. First, it shows that in a large subset of adult pa ents airway eosinophilia can be iden ed with high certainty by using FeNO and blood eosinophils instead of induced sputum. Second, it shows that the accuracy of these biomarkers is similar in various subtypes and severi es of asthma. Currently, FeNO and blood eosinophils are mainly used in clinical trials to iden fy pa ents with eosinophilic asthma who are eligible for treatment with novel targeted therapies. For example for mepolizumab, a blood eosinophil cuto >0,15*10^9/L was introduced to detect eosinophilic asthma and predict reduc on of asthma exacerba ons 35. Our data show that this is an adequate threshold to detect eosinophilia, since an eosinophil count <0.09*10^9/L is associated with absence of airway eosinophilia in 92% of the pa ents. S ll, consensus about the respec ve biomarker thresholds is needed, as well as an algorithm and external valida on that incorporates a combina on of biomarkers.
In conclusion, we showed that FeNO and blood eosinophils have a comparable diagnos c accuracy to iden fy airway eosinophilia in adult asthma pa ents irrespec ve of phenotypic characteris cs such as asthma severity, atopy, obesity and smoking status, and, possibly, irrespec ve of underlying pathways leading to airway eosinophilia. In future clinical trials and day-to-day prac ce both markers, preferably in combina on, may become the preferred method to assess eosinophilic airway in amma on and to guide targeted treatment in adult asthma pa ents with di erent phenotypes.
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