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Persistence of Airway Obstruction and Hyperresponsiveness in Subjects With Asthma Remission: Methods

Published in Asthma

Subjects
Sixty-five subjects took part in this study (Table 1). Of these, 30 ex-asthmatics were recruited from advertisements in different media.
Inclusion Criteria and Definition of Asthma Remission
We included in the study men or women >18 years old, atopic or not, with a proven history of asthma responding to the American Thoracic Society criteria, who were considered to be in asthma remission for at least 2 years. “Remission” of asthma was defined according to the definitions of Bronnimann and Burrows: “asthma was considered to be inactive (ex-asthma) if the subject denied medications, asthmatic attacks, and ‘frequent’ (more than two) attacks of shortness of breath with wheezing during the preceding year.” We, however, extended the minimum period of symptom remission to 2 years, to be included in the study.
We considered that our subjects had “proven asthma” according to the following criteria: all had a history of dyspnea and wheezing in the past; 26 subjects had a diagnosis of asthma made by a physician; 16 had previous available chart recordings of typical asthma presentation and wheezing on chest auscultation; 27 had used antiasthma medications (mostly bronchodilators) for different periods of time; and physiologic data showing airflow obstruction were available in 10 subjects. Furthermore, ten subjects had been hospitalized previously for their asthma and five had required mechanical ventilation for acute asthma.
Exclusion Criteria
We excluded the subjects with chronic bronchitis, emphysema, or other pulmonary diseases, or with a significant smoking history (>5 pack-years of cigarettes). canadian drug mall

Control Group
Ex-asthmatics were individually matched for age, sex, and presence of atopy to a control group of subjects without past or present history of asthma or any other respiratory condition (Table 2). These subjects were naive controls, recruited from advertisements in the same media as ex-asthmatics. Five of the subjects who volunteered as controls were included in the study following initial evaluation, although they had asthma symptoms that were. not recognized as such, and showed airway hyperresponsiveness, with а РС20» the provocative concentration of methacholine inducing a 20 percent fall in forced expiratory volume in one second (FEVi), ranging from 1.7 to 7.0 mg/ml. The results presented concern these first 30 control subjects. To add comparisons of ex-asthmatics to a control population without airway hyperresponsiveness, the 5 control hyperreactive subjects were replaced, in a second set of analysis, to complete the matching of ex-asthmatics with 30 normoresponsive controls. The study was approved by our local Ethics Committee and all subjects signed an informed consent form.

Table 1—Subjects Characteristics

Asthma “in Remission” Controls
No. of subjects 30 (20M, 10F) 30 (20M, 10F)
Age, yr, mean (range) 32.1 (18 to 61) 31.6 (20 to 67)
Atopy, No. of subjects 28 28
No. of positive responses 8.8 (0 to 20) 7.9 (0 to 20)
Past immunotherapy 10 2
Age at the onset of asthma, yr, mean±SEM (range) 10.5 ±1.8 (0 to 33)
Duration of symptomatic asthma, yr, mean±SEM (range) 12.4 ±1.7 (2 to 33)
Duration of remission, yr, mean ± SEM (range) 9.6 ±1.3 (2 to 25)
Family history of asthma 11 10
Family history of atopy 16 21

Table 2—Expiratory Flows, Lung Volumes, Response to Bronchodilators, and Diurnal Changes in PEFR (Means Percent Predicted Value or Percent Change ±SEM)

Ex-Asthmatics(N=30) Controls(InitialSubjects)(N=30) Controls (5 Hyperreactive Subjects Replaced) (N=30)
Expiratory flows
FEV! 91.0 ±2.5 104.1 ±1.9 103.9 ±2.0
FVC 97.8 ±2.3 104.0±1.8 103.6± 1.9
FEF25-75% 70.6 ±4.8 89.0 ±4.0 89.8 ±4.0
FEVi/FVC 93.3 ±1.7 100.2 ±0.9 100.7 ±1.0
Lung volumes
RV 140.7 ±8.0 118.8±5.7 119.2 ±5.7
FRC 113.6 ±5.6 99.4 ±3.6 98.9 ±3.7
Response to
bronchodilators
AFEVi 5.7 ±0.8 2.5 ±0.6 2.3 ±0.5
AFEF25-75% 17.3 ±2.6 13.5 ±2.3 11.7 ±1.8
Diurnal changes
in PEFR, %
Maximum APEFR 12.3 ±1.3 7.0 ±0.8 7.3 ±1.0
Mean APEFR 4.6 ±0.4 2.9 ±0.3 2.9 ±0.4