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Reconcilable Differences: Statistical Analysis

Published in Asthma

Three interval score measures of asthma severity, each based on different dimensions of asthma severity, were also used. The asthma symptom sum (ASS) is a summed score of patient-rated severity of wheeze, shortness of breath, cough, and chest tight-ness. The chronic lung disease severity index (CLDSI) is a validated summed score proposed for use in asthma, emphysema, and chronic bronchitis derived from the frequency ofshortness of breath, wheeze, cough, and sputum production. Each component of the ASS and CLDSI is included in the AQLQ(S). Therefore, these scores were derived from the corresponding AQLQ(S) questions, resulting in final severity scores ranging from 4 to 28, with higher scores representing less severe disease.
Ng proposed a score (referred to as the Ng Score) ranging from 3 (least severe) to 10 based on the frequency of daytime and nocturnal symptoms, and the percentage of predicted FEV1. Final scores were reverse coded to correspond with the direction of the ASS and CLDSI.

Finally, a specific model incorporating all variables related to each proposed dimension of asthma severity was developed with the amount of SA P-agonist use as the dependent variable. Initially, separate models were developed for the dimensions of symptoms, morbidity, airway obstruction, and asthma medication use (other than SA P-agonists) using forward stepwise multiple polychotomous logistic regression. All significant variables from each dimension model were then incorporated into a final forward stepwise regression model, yielding a final model of all severity-related factors that best explained the magnitude of SA P-agonist use. natural breast enhancement
The relationship between SA P-agonist use and SES, controlling for asthma severity, was evaluated using polychoto-mous logistic regression. The dependent variable was the ordinally classified number of standardized canisters of SA P-agonist used in the previous year. Each individual was classified as a low (< 4 canisters), intermediate (4 to 12 canisters), or high (> 12 canisters) user. A cumulative logit model was used that assumes that the log-cumulative odds are proportional, or that the odds of a response above a given response level are constant, independent of the cut point chosen. To ensure the maximal explanation of the variance of SA P-agonist use attributable to asthma severity, any dimension of severity not included in a specific severity score was added to the model prior to adding the SES variable, and prior to the evaluation of all potential interactions.