title: Developing an item bank and short forms that assess the impact of asthma on quality of life.
abstract: The present work describes the process of developing an item bank and short forms that measure the impact of asthma on quality of life (QoL) that avoids confounding QoL with asthma symptomatology and functional impairment. Using a diverse national sample of adults with asthma (N = 2032) we conducted exploratory and confirmatory factor analyses, and item response theory and differential item functioning analyses to develop a 65-item unidimensional item bank and separate short form assessments. A psychometric evaluation of the RAND Impact of Asthma on QoL item bank (RAND-IAQL) suggests that though the concept of asthma impact on QoL is multi-faceted, it may be measured as a single underlying construct. The performance of the bank was then evaluated with a real-data simulated computer adaptive test. From the RAND-IAQL item bank we then developed two short forms consisting of 4 and 12 items (reliability = 0.86 and 0.93, respectively). A real-data simulated computer adaptive test suggests that as few as 4-5 items from the bank are needed to obtain highly precise scores. Preliminary validity results indicate that the RAND-IAQL measures distinguish between levels of asthma control. To measure the impact of asthma on QoL, users of these items may choose from two highly reliable short forms, computer adaptive test administration, or content-specific subsets of items from the bank tailored to their specific needs.
authors.affiliation: RAND Corporation, Santa Monica, CA 90407, USA. Electronic address: bstucky@rand.org.
authors.forename: Brian D
authors.initials: BD
authors.lastname: Stucky
authors.affiliation: RAND Corporation, Boston, MA 02116, USA.
authors.forename: Maria Orlando
authors.initials: MO
authors.lastname: Edelen
authors.affiliation: RAND Corporation, Santa Monica, CA 90407, USA.
authors.forename: Cathy D
authors.initials: CD
authors.lastname: Sherbourne
authors.affiliation: RAND Corporation, Santa Monica, CA 90407, USA.
authors.forename: Nicole K
authors.initials: NK
authors.lastname: Eberhart
authors.affiliation: RAND Corporation, Santa Monica, CA 90407, USA.
authors.forename: Marielena
authors.initials: M
authors.lastname: Lara
mesh_terms: D000293:Adolescent; D000328:Adult; D001249:Asthma / Q000517:prevention & control / Q000523:psychology*; D003198:Computer Simulation; D005163:Factor Analysis, Statistical; D006801:Humans; D062072:Patient Acuity; D011788:Quality of Life; D012680:Sensitivity and Specificity; D011795:Surveys and Questionnaires / Q000592:standards; D055815:Young Adult
keywords: Asthma; Health-related quality of life; Item bank; Item response theory; Psychometrics; RAND-IAQL