Exploring asthma control cutoffs and economic outcomes using the Asthma Control Questionnaire.

BACKGROUND: Understanding the effect of worsening asthma control on expenditures and health resource utilization (HRU) is important.

OBJECTIVE: To explore the association of economic outcomes with asthma control cutoffs and longitudinal changes on the Asthma Control Questionnaire 5 (ACQ-5).

METHODS: The Observational Study of Asthma Control and Outcomes was a survey of patients with persistent asthma who were patients of Kaiser Colorado, including claims-based HRU. Patients completed the ACQ-5 three times during 1 year between April 2011 and June 2012. The ACQ-5 cutoffs that indicated control were assessed in cross-sectional analyses. Longitudinal changes in control were explored: controlled (ACQ-5 score <0.75), indeterminate (ACQ-5 score 0.75 to <1.5), not well controlled (ACQ-5 score 1.5 to <3.0), and very poorly controlled (ACQ-5 score ≥3.0). Analyses used generalized linear models with log link (expenditures) and negative binomial regression (HRU).

RESULTS: There were 6,666 completed surveys (1,799 individuals completed all 3 survey waves). In the cross-sectional analyses, compared with an ACQ-5 score less than 0.5, individuals with ACQ-5 scores of 4 to 4.5 incurred 7.2 times the number of oral corticosteroid prescriptions, 4.3 times the number of emergency department visits, 6 times the number of inpatient visits, 10.4 times the number of asthma-specific emergency department visits, 4.58 times the number of asthma-specific inpatient visits, and $2,892 more in all-cause and $1,877 in asthma-specific expenditures during 4 months. In the longitudinal change analyses, individuals who improved from an ACQ-5 of 3.0 or greater to less than 0.75 incurred $6,023 less in asthma-specific expenditures during 4 months than those remaining at an ACQ-5 score of 3.0 or higher.

CONCLUSION: Results provide preliminary economic data on possible control cutoffs for the ACQ-5. Improving asthma control over time may result in significant savings that may justify financial investments designed to improve control.