Extent, patterns, and burden of uncontrolled disease in severe or difficult-to-treat asthma.
BACKGROUND
Characterization of uncontrolled asthma burden in a natural treatment setting can influence treatment recommendations and clinical practice. The objective was to characterize and compare the economic burden of severe or difficult-to-treat asthma in uncontrolled and controlled patients.


METHODS
Baseline patient data (age > or = 13 years; n = 3916) were obtained from The Epidemiology and Natural History of Asthma: Outcomes and Treatment Regimens study. Disease control was assessed using two approaches: (i) applying criteria for control based on the Gaining Optimal Asthma Control study, and (ii) using the Asthma Therapy Assessment Questionnaire (ATAQ) to identify the number of asthma control problems. Assessments were performed at baseline, and at months 12 and 24. Monetary values were assigned to productivity loss and medical resource use. Direct and indirect costs were aggregated over 24 months and compared using Student's t-test for continuous measures and chi-squared for categorical variables.


RESULTS
Throughout the study, most patients had uncontrolled asthma (83% uncontrolled; 16% inconsistent control; 1.3% controlled). Controlled patients experienced fewer work or school absences and less healthcare resource use than uncontrolled patients at all study time points. Using the multilevel ATAQ control score, asthma costs increased directly with the number of asthma control problems. Costs for uncontrolled patients were more than double those of controlled patients throughout the study (14,212 vs 6,452 US Dollars; adjusted to 2002 Dollars; P < 0.0001).


CONCLUSIONS
This study demonstrated that few severe or difficult-to-treat asthma patients achieved control over a 2-year period and the economic consequence of uncontrolled disease is substantial.