Reconcilable Differences: Asthma Severity
Both individual (proximate) and population (contextual) measures of SES were used. Proximate measures were based on self-reported annual household income ($20,000, $20,000 to $50,000, and >$50,000, expressed in Canadian dollars), education (years of postsecondary education and highest level completed), and the receipt of social assistance. Exploratory analysis accounting for family size based on the low-income cutoff was also performed. Contextual socioeconomic factors, ie, neighborhood median household income, unemployment rate, and the proportion of residents having received a bachelor’s degree, were derived from the linkage of the postal code of each subject’s current residence with the 1996 BC census data.
Blood was collected from each subject for DNA extraction from leukocytes. Genotyping for P2-adrenergic receptor polymorphisms at positions 16 and 27 was done using polymerase chain reaction amplification of the region containing the two polymorphisms followed by restriction endonuclease digestion. The associations between genotype and the amount of SA P-agonist used were compared separately for each locus. Homozygotes for arginine and glycine at position 16 and glutamine at position 27 were compared separately to all other individuals. more
Four dimensions of asthma have been proposed as measures of asthma severity: symptoms, medication use, degree of airflow obstruction, and asthma-related morbidity (eg, emergency department visit or hospital admission); however, there is currently no “gold standard” for measuring asthma severity. Therefore, we used five different methods to facilitate comparison.
An algorithm based on the Canadian Asthma Guidelines, including whether or not asthma was controlled, asthma medication use (other than SA P-agonists), the degree of airflow obstruction, and symptoms was used to classify asthma severity as mild, moderate, or severe. The magnitude of asthma symptoms was derived from the scores on the symptom and activity domains of the Standardized Asthma Quality of Life Questionnaire (AQLQ[S]).