Page 47 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

BIOMARKERS TO IDENTIFY SPUTUM EOSINOPHILIA IN DIFFERENT ADULT ASTHMA PHENOTYPES
REFERENCE STANDARD: SPUTUM EOSINOPHILS
Sputum induc on was performed according to interna onally accepted standards by trained lung func on analysts 24. All pa ents inhaled a nebulized saline solu on for 5 minutes, if possible repeated up to 3 mes. Sputum processing was performed according to full sample method and di eren al cell counts were analyzed on cytospin prepara ons. Results for di erent sputum cell types are presented as percentage of total non-squamous cell count. Laboratory analyses were performed blinded to pa ent characteris cs and index test results.
INDEX TESTS: FENO, BLOOD EOSINOPHILS AND TOTAL IGE
FeNO (index test 1) was measured with a portable rapid-response chemoluminescent analyser ( ow rate 50mL/s; NIOX System, Aerocrine, Sweden). FeNO results are reported as parts per billion (ppb) 25.
Venous blood was collected and di eren al white blood cells counts were performed. Absolute blood eosinophil numbers (index test 2) are reported as 10^9 cells per liter. Total IgE (index test 3) was measured by ImmunoCAP and reported as Ku/L. All measurements in blood samples were performed by the general laboratories of the par cipa ng hospitals and blinded to the outcome of other tests.
All data were collected in 1-2 visits less than 2 weeks apart.
STATISTICAL ANALYSIS
Adequate sputum samples from 336 pa ents were available (Figure E1, Study owchart) and these pa ents were included in the analyses of diagnos c accuracy. Baseline characteris cs between pa ents with and without adequate sputum were compared . Pa ents with missing data on blood esoinophils, FeNO or total IgE were excluded for the analysis of that index test.
Receiver operator characteris cs curve (ROC) analysis was used to evaluate the diagnos c accuracy of FeNO, blood eosinophils, total IgE and their combina ons to iden fy sputum eosinophilia ≥3%. This was done rst in the complete group and therea er in subgroups with speci c phenotypic pa ent characteris cs as described above. Analysis included the following: a) area under the ROC curve (AUC) (95% con dence interval (95%CI)) for the di erent biomarkers (FeNO, blood eosinophils, total IgE), b) sensi vity (95%CI) and corresponding threshold of each biomarker at a speci city of ≥95%, and c) speci city (95%CI) and corresponding threshold of each biomarker at a sensi vity of ≥95%. McNemar test was used to compare sensi vi es and speci ci es between biomarkers. DeLong tests were used to compare AUC’s between di erent asthma phenotypes and to evaluate whether combina ons of any of the three biomarkers improved the diagnos c accuracy of each single biomarker.
We also developed a mul variate logis c regression model for the predic on of sputum eosinophilia ≥3% based on phenotypic features and the three markers. First, we evaluated whether pa ent characteris cs (age, sex, BMI, asthma dura on, race, smoking status, FEV1 post bronchodilator, FEV1/FVC post bronchodilator, atopy status, medica on use (high dose
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