Page 146 - ADULT-ONSET ASTHMA PREDICTORS OF CLINICAL COURSE AND SEVERITY

ADULT-ONSET ASTHMA – PREDICTORS OF CLINICAL COURSE AND SEVERITY
METHODS
STUDY DESIGN AND PARTICIPANTS
This was a cross-sec onal study using pooled baseline-data from three observa onal cohort studies with similar methodologies. These three studies included in total 571 pa ents with adult-onset asthma between 2009 and 2012 (Netherlands Trial Register numbers: NTR2217, NTR1846 and NTR1838) and aimed at phenotyping pa ents based on an extensive set of clinical, func onal and in ammatory parameters. All three trials were reviewed and approved by medical ethical boards before their ini a on.
Adult pa ents were eligible for the three cohorts if they had a con rmed diagnosis of asthma with onset of the disease a er the age of 18 years. Asthma diagnosis was based on a history of variable respiratory symptoms AND documented variable expiratory air ow limita on: reversibility in FEV1 of >12 % predicted and 200 ml or airway hyperresponsiveness to inhaled methacholine (PC20 <8 mg/ml) or diurnal varia on in PEF of ≥20% or history of prompt deteriora on in FEV1 a er ≤25% reduc on in oral or inhaled cor costeroid dose (within 4 weeks).1 Pa ents with other pulmonary diseases, non-related major co-morbidi es, and pregnancy were excluded. Smoking was allowed, however, pa ents with a smoking history of > 10 pack years combined with xed air ow obstruc on and/or reduced di usion capacity (DLCO/VA <80%) were excluded. Detailed in- and exclusion criteria have been reported previously.10-12 All pa ents were informed and gave wri en consent.
For the present study pa ents with severe asthma were selected (see Figure 1 for study owchart); those using high intensity asthma treatment as de ned by GINA treatment step 4-5 (use of high dose inhaled cor costeroid and a second controller or systemic cor costeroid use >50% of the previous year)1 and with uncontrolled asthma de ned as either asthma control ques onnaire (ACQ)-score >1.5, 2 or more exacerba on per year or presence of air ow limita on with an FEV1 <80% predicted.13
A er that, pa ents were stra ed according to smoking status: current smokers and ex- smokers were combined into one group called (ex)smokers,11 their smoking history was quan ed by calcula ng the number of pack years. Never smokers were pa ents who had never smoked.
Finally, (ex)smokers and never smokers were divided in two groups: 3 or more exacerba ons (frequent exacerbations) or ≤ 1 exacerbations in the previous year (non-frequent exacerba ons) as previously reported.14,15 An asthma exacerba on was de ned as an increase in asthma symptoms requiring treatment with a course of oral cor costeroids (OCS) or at least a doubling from a stable maintenance dose for at least three days. Courses of systemic cor costeroid separated by one week or more were recorded as a separate exacerba on.
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