The Relationship of Asthma Impairment Determined by Psychometric Tools to Future Asthma Exacerbations
Methods: Two thousand six hundred eighty patients with persistent asthma completed a survey that included the Asthma Control Test (ACT), mini-Asthma Quality of Life Questionnaire (mAQLQ), and Asthma Impact Survey (AIS-6), as well as a history of exacerbations in the prior 12 months. An exploratory factor analysis was performed using the questions of the three tools, and individual patient factor scores were calculated. Independent relationships between predictors (tools and factors) and exacerbations the following year captured from administrative data were evaluated.
Results: Each tool was significantly related (P < .0001) to future exacerbations above and beyond the risk conferred by prior exacerbations (relative risk [RR] = 1.3). When prior exacerbations were included in the model, the three impairment tools provided similar and overlapping information, such that only the mAQLQ entered the model (RR = 1.3; 95% CI, 1.1-1.5). Factor analysis revealed three factors (symptoms, activity, and bother) that were each significantly associated (P < .0001) with future asthma exacerbations. However, only the activity factor was independently related to future exacerbations.
Conclusions: Asthma impairment is significantly related to the risk of future exacerbations, but the ACT, mAQLQ, and AIS-6 do not provide independent information from each other in this regard. Interference with activities is the primary subjective component of asthma impairment that is related to the risk of future exacerbations.
Abbreviations: ACT = Asthma Control Test; AIS-6 = Asthma Impact Survey; mAQLQ = mini-Asthma Quality of Life Questionnaire; PPV = positive predictive value
Asthma causes a spectrum of morbidity, ranging from symptoms to functional impairment to exacerbations. Factor analysis studies have suggested that asthma exacerbations represent a separate dimension from symptoms, quality of life, and pulmonary function. Partly in response to these data, the new National Asthma Education and Prevention Program Expert Panel 3 guidelines divide asthma severity and control into two domains: impairment and risk.