Development and psychometric properties of the Pulmonary-specific Quality-of-Life Scale in lung transplant patients

Abstract

The Pulmonary-specific Quality-of-Life Scale (PQLS) was developed to measure quality of life (QoL) among patients awaiting lung transplant. The objective of this study was to determine the psychometric properties of the PQLS, identify empirically derived sub-scales, and examine ability to detect changes in pulmonary-specific QoL scores after lung transplantation. Data were derived from the INSPIRE trial, a dual-site randomized controlled trial of coping skills training in 389 lung transplant candidates (obstructive [48.3%], restrictive [24.2%], cystic fibrosis [13.6%], and other [13.9%]). Cronbach alpha was calculated to assess the internal reliability of the PQLS (n = 388). Test-retest reliability was assessed with correlation coefficients between baseline and 12-week post-baseline scores for the usual care control condition (n = 140). Convergent validity was assessed with correlation coefficients between the PQLS and established measures of QoL and emotional distress, 6-minute walk test distance, forced expiratory volume in 1 second, and use of supplemental oxygen at rest (n = 388). Change from baseline to 6 months post-transplantation was assessed with repeated measures analysis of variance (n = 133). The PQLS was internally reliable and stable across 12 weeks. The PQLS correlated strongly with QoL measures (e.g., Shortness of Breath Questionnaire, r = 0.78, p < 0.0001), moderately with mood and anxiety (e.g., Beck Depression Inventory-II, r = 0.59, p < 0.0001), and modestly with lung disease severity (e.g., 6-minute walk test, r = -0.41, p < 0.0001). PQLS scores improved by nearly 2 SDs after transplant. These results demonstrated the reliability, validity, and sensitivity to change of the PQLS for measuring pulmonary QoL among patients with advanced lung disease and the responsiveness of the PQLS to changes in QoL after lung transplantation.