Existing asthma-related quality of life (QoL) scales do not directly assess QoL or the perceived impact of asth- ma on QoL. The purpose of this study is to evaluate the psychometric properties (reliability, concurrent and longitudinal validity, and responsiveness to change in asthma status) of a new measure of the patient- perceived negative effects of asthma in adults, the Asthma Impact on Quality of Life Scale (A-IQOLS), and to compare its properties with those of a measure of current QoL, the Flanagan Quality of Life Scale (QOLS). We hypothesize that the approach represented by the A-IQOLS will prove superior to that of the QOLS as an out- come measure for clinical research. This research can fill a significant gap in the currently available tools, with consequent benefit to asthma clinical research and, potentially, measurement of patient-centered outcomes in other disease areas.
Measurement of disease effects on patients'quality of life (QoL) can inform clinical management, health care policy, and evaluation of new therapies. Existing asthma-related QoL scales do not directly assess either QoL or the perceived impact of asthma on QoL. The 2010 NIH Asthma Outcomes Workshop called for new measures that assess the perceived impact of asthma on QoL. We have developed a new tool, the Asthma Impact on Quality of Life Scale (A-IQOLS), which utilizes the Flanagan QoL dimensions plus one added by Burckhardt. The AIQOLS approach is straightforward but novel;adult respondents rate the negative effect of their asthma on each of 16 QoL dimensions. The A-IQOLS summary score (mean of the individual dimension ratings), is higher when the effect of asthma is more negative and/or affects more dimensions of the individual's life. This study's purpose is to evaluate the psychometric properties of the A-IQOLS, including its sensitivity to change or group differences in asthma status, and to test the hypothesis that A-IQOLS is more sensitive than a measure of current QoL, the Flanagan QOLS, which uses the same dimensions and has been used in clinical research but not in asthma. We hypothesize that the A-IQOLS will meet statistical criteria justifying its use as an outcome measurement tool, and that weighting A-IQOLS dimension ratings by that dimension's importance to the individual, using the individual's QOLS-Importance ratings, will not improve summary score reliability and responsiveness sufficiently to offset the disadvantages of response weighting. We will carry out exploratory analyses to estimate the path coefficients of a statistical model of the perceived impact of asthma on QoL and to answer other questions regarding the factors that influence patients'QoL and the perceived impact of asthma on their QoL. The performance characteristics of the A-IQOLS and QOLS scores will be compared in asthma patients 18 years of age and older. Data on both instruments, as well as Juniper AQLQ scores and other measures of asthma status, will be collected in an observational study with a brief follow-up (test/retest) to be conducted in a broad sample of patients with persistent asthma who are receiving care from the Palo Alto Medical Foundation (n=145). The A-IQOLS and QOLS also are being administered in three additional studies being conducted throughout the United States: a randomized control trial of step-down therapy in patients with well-controlled asthma (n=450), a trial of continuous positive airway pressure (CPAP) to reduce airway hyper-reactivity in asthma (n=192), and a prospective study to characterize responders to bronchial thermoplasty in patients with asthma refractory to conventional therapy (n=190). This study can fill a significant gap in the tools available to assess patient-centered asthma outcomes. The knowledge it yields will directly benefit asthma clinical research and will have broad implications for measurement of the impact of other diseases and of overall health status.