Page 49 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

BIOMARKERS TO IDENTIFY SPUTUM EOSINOPHILIA IN DIFFERENT ADULT ASTHMA PHENOTYPES
RESULTS
Table I shows baseline characteris cs of the 336 pa ents who were included in the analyses. Compared to these pa ents, the excluded pa ents (n=235) were younger, more o en female and had slightly lower blood eosinophils (Table E1). Sputum eosinophilia was present in 116 pa ents (35%). FeNO, blood eosinophils and total IgE were missing in 10, 5 and 4 included pa ents, respec vely. Correla ons of the three biomarkers with sputum eosinophils are shown in Figure E2.
DIAGNOSTIC ACCURACY OF BIOMARKERS
In the complete group as well as in the 8 subgroups, FeNO and blood eosinophils had similar diagnos c accuracy, whereas the AUC for total IgE was signi cantly lower (Tables 2 and 3). Combining FeNO and blood eosinophils signi cantly improved diagnos c accuracy compared to FeNO alone (p=0.001) or blood eosinophils alone (p=0.027) (AUC 0.87 (95%CI 0.83-0.91),Table 2-3, Figures 1-2). Adding total IgE to the combina on of FeNO and blood eosinophils did not signi cantly improve the AUC (0.87, p=0.732). Total IgE performed signi cantly be er in obese than in non-obese pa ents, and in non-atopic compared to atopic pa ents, respec vely (Table 3, Figure 2).
A mul variable logis c model was created and reduced using stepwise backward selec on. The nal model included age, sex, FEV1/FVC, pulmonary medica on (high or low ICS dose), FeNO and blood eosinophils (Table E2). This model further improved the diagnos c accuracy to a minimal extend compared to FeNO and blood eosinophils combined (AUC 0.89 (95%CI 0.85-0.93), p=0.041).
Sensi vity, speci city and biomarker thresholds
Table 2 shows the sensi vity and speci city for each biomarker at either a high speci city or sensi vity and the associated threshold of this marker; Figure E3 shows the formula to calculate the probability of sputum eosinophilia for the combined model of FeNO and blood eosinophils.
At a sensi vity of ≥95% (i.e. low number of false nega ves) FeNO, blood eosinophils and total IgE had a comparable speci city, whereas the speci city of FeNO and blood eosinophils combined was signi cantly higher. Nega ve predic ve values ranged between 0.92 and 0.94 for biomarker values below the corresponding thresholds.
At a speci city of ≥95% (i.e. low number of false posi ves) sensi vi es for FeNO, blood eosinophils and their combina on did not signi cantly di er, but the sensi vity of total IgE was signi cantly lower compared to the other biomarkers. The posi ve predic ve values of FeNO, blood eosinophils and their combina on ranged from 0.79 to 0.84, but was only 0.47 for total IgE.
With these thresholds (Table 2), the biomarkers can be used in up to half of the pa ents,
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