Determinants of Percent Predicted FEVi in Current Asthmatic Subjects: Methods


The present study is a cross-sectional analysis from survey 1 and is based on those subjects who stated on their initial questionnaire that they had ever had asthma and who either: (1) stated that they “still had it/’ (2) had more than rare “attacks of shortness of breath with wheezing,” (3) reported “wheezing or whistling” in the chest even apart from colds,” or (4) were taking medication or treatment for their asthma. Current asthmatic subjects more than 40 years of age with a physician’s diagnosis of emphysema and at least a 20 pack-year history of smoking were excluded from this analysis. Allergy skin testing was done on subjects age 3 years and older, while blood for eosinophil counts and IgE measurement was drawn on subjects age 6 years and older. Acceptable spirometry at the time of the initial questionnaire was available on 261 asthmatic subjects 6 to 88 years of age. Methods of allergy skin testing, eosinophil counting, and measurement of serum IgE level have been reported before.

Predicted values for spirometric values were derived from regression equations by sex on normal subjects in this population sample. Natural asthma treatment read only Independent variables in these equations included age and height. As in previous reports on the Tucson subjects, IgE levels are expressed as Z-scores, with the score being the number of standard deviations by which a subjects log IgE level differs from the mean log IgE for his or her age-sex specific group of those initially enrolled in the Tucson study.
A wheeze scale was derived from the severity of wheezing and the frequency of attacks of shortness of breath with wheezing. Those with only rare “attacks” of wheeze apart from colds were given a wheeze scale grade of 1+ (mild), and the wheeze scale increased with severity so that those with attacks of shortness of breath on most days with or without wheeze most days were given a grade of 5+ (severe). Statistical methods include analysis of variance, x2 test, t test, and multiple regression analysis using SPSS statistical software.