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

doi:10.1016/j.anai.2016.07.020

Annals of Allergy, Asthma & Immunology

Volume 117, Issue 3, September 2016, Pages 251-257.e2

https://doi.org/10.1016/j.anai.2016.07.020 Get rights and content

Abstract

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.

Introduction

Asthma guidelines have focused on maintaining and improving asthma control as the goal of therapy and have categorized control into 3 levels: controlled or well controlled, partially controlled or not well controlled, and uncontrolled or very poorly controlled.[1], [2] Several instruments have been developed to measure asthma control. One example, the Asthma Control Questionnaire (ACQ) has been used extensively as a standardized measure³ and has been designated as a core measure for research supported by the National Institutes of Health in adults.⁴ Developers have conducted investigations to determine the cutoff points of the ACQ that correspond to different levels of control. Established cutoffs include controlled asthma (ACQ score ≤0.75) and uncontrolled asthma (ACQ score ≥1.5).⁵ There is no clear evidence for the ACQ score cutoff to distinguish between not well controlled and very poorly controlled corresponding to the guideline-based levels above.⁶

Economic outcomes are an important part of optimizing asthma treatment given the reality of limited financial resources. According to the Global Initiative for Asthma, the main goal of asthma treatment is to achieve control and reduce risk of future exacerbations with regard to the cost of treatment.² To understand the true effect of treatment, it is imperative to comprehensively understand the economic effect of changes in asthma control. A promising new asthma management program or intervention may result in improved control, but is it financially viable? Knowledge of the economic effect of improving asthma control is essential to answering this question.

Asthma results in increased health resource utilization (HRU) and expenditures.[7], [8] In particular, poorly controlled asthma has a significant negative effect on HRU and expenditures compared with adequately controlled asthma, and patients with the most severe disease account for most of the cost.[9], [10], [11], [12] Increasing scores (worsening asthma control) on the ACQ-5 (a 5-item patient-reported questionnaire about asthma symptoms) are strongly associated with increased HRU, expenditures, and risk of exacerbations in cross-sectional analyses of a general population of individuals with persistent asthma.¹³ However, little is understood about the association between clinical cutoff points of asthma control and economic outcomes. In addition, previous research on the economic effect of asthma control has been based on cross-sectional associations not longitudinal changes over time. Cross-sectional associations do not incorporate within-person improvement or deterioration over time. Given limited longitudinal estimates, most cost-effectiveness studies are forced to assume that cross-sectional associations are good proxies of actual longitudinal changes. Because all asthma interventions aim to improve control over time, longitudinal analyses are the most accurate means of estimating their effect. The purposes of this research are to explore the association of economic outcomes with cutoff points in asthma control via the ACQ-5 and to quantify the economic effect of changes in control level over time (ie, from very poorly controlled to controlled).

Section snippets

Data Source

The Observational Study of Asthma Control and Outcomes (OSACO) was a prospective survey and retrospective claims-based analysis of patients with persistent asthma 12 years or older who where patients of Kaiser Permanente of Colorado (KPCO).¹³ Eligible patients were sent surveys during 3 waves during 1 year between April 2011 and June 2012. The survey included questions on asthma control (ACQ-5), smoking status, sex, family income level, race, educational attainment, and ethnicity.

HRU and

Cross-sectional Analyses

Unadjusted HRU and expenditures by ACQ-5 scores cut by 0.5 are presented in Table 1. All measures of HRU and expenditures increased with increasing ACQ-5 scores. There were few individuals with ACQ-5 scores greater than 4.5, and estimates are much less consistent for these categories. Individuals with ACQ-5 scores between 4 and 4.5 filled 1.4 prescriptions for short-acting β-agonists (SABAs), had 3 outpatient visits (1.1 with asthma diagnosis), and incurred $7,298 (all-cause) and $4,108

Discussion

This research suggests that there is an economic benefit to improving asthma control over time in a general population. For example, improving patients progressing from very poorly controlled to controlled asthma resulted in a savings of $6,000 (4-month cost). In addition, this research reveals a strong association between greater HRU and expenditures and common cutoff points for poor control on the ACQ-5. It also provides preliminary information about which ACQ-5 points may be relevant cutoffs

Acknowledgment

We thank Denise Globe, PhD, for her valuable contribution to the conception and design of the study.

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: Disclosures: Dr Sullivan reported receiving research grants from Amgen Inc. Dr Globe reported being an employee of Amgen Inc. No other disclosures were reported.

: Funding Sources: This study was funded by a research grant from Amgen Inc.

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Original articleAsthma, lower airway diseasesExploring asthma control cutoffs and economic outcomes using the Asthma Control Questionnaire

Abstract

Background

Objective

Methods

Results

Conclusion

Introduction

Section snippets

Data Source

Cross-sectional Analyses

Discussion

Acknowledgment

J Allergy Clin Immunol

Respir Med

J Allergy Clin Immunol

J Allergy Clin Immunol

Ann Allergy Asthma Immunol

Respir Med

J Allergy Clin Immunol

Expert Panel Report: Guidelines for the Diagnosis and Management of Asthma Update on Selected Topics–2002

J Allergy Clin Immunol

Original article
Asthma, lower airway diseases
Exploring asthma control cutoffs and economic outcomes using the Asthma Control Questionnaire