The Oort structural equation modeling approach detected a response shift after a COPD self-management program not detected by the Schmitt technique Sara Ahmed a, * , Jean Bourbeau a,b , Franc ¸ois Maltais c , Asmaa Mansour a a Faculty of Medicine, McGill University, Montr eal, Qu ebec, Canada b Respiratory Epidemiology and Clinical Research Unit, Montreal Chest Institute, McGill University Health Centre, Montr eal, Qu ebec, Canada c Centre de recherche, H^ opital Laval, Institut Universitaire de Cardiologie et de Pneumologie de l’Universit e Laval, Qu ebec, Canada Accepted 16 March 2009 Abstract Objective: If individuals experience a response shift, scores on measures before and after a self-management intervention may not be comparable. This study evaluated whether persons with chronic obstructive pulmonary disease (COPD) experience a response shift after participating in a self-management program. The second objective was to compare the Oort and Schmitt structural equation modeling (SEM) approaches. Methods: Secondary analyses from a randomized controlled trial comparing a home- and hospital-based pulmonary rehabilitation pro- gram were used to assess response shift on a physical and mental healthemeasurement model measured using the Chronic Respiratory Questionnaire (CRQ) and the St. George’s Respiratory Questionnaire (SGRQ) over a 1-year period. Results: The Oort approach showed significant changes between the no response shift model and models removing invariance con- straints for the residual of the CRQ dyspnea (c 2 SBdiff 5 7, df 5 1) (uniform recalibration) and intercepts of the SGRQ activity (c 2 SBdiff 5 14, df 5 1) and impact (c 2 SBdiff 5 10, df 5 1) subscales (nonuniform recalibration). Change in factor means showed changes in the physical health factor, which was slightly lower in unadjusted (0.32) as compared with the response shifteadjusted model (0.40). The Schmitt pro- cedure was not supportive of any response shift effect and showed a marginal change in random error over time. Conclusions: This study showed that COPD patients experienced a response shift after participating in a self-management program, which resulted in an underestimation of change in physical health. These results suggest that the Oort procedure is more sensitive in detect- ing a response shift, and that a measurement of response shift is needed before results can be interpreted. Future comparisons with other methods and a control group are needed. Ó 2009 Elsevier Inc. All rights reserved. Keywords: Self-management; Adaptation; Coping; Change; Quality of life; Structural equation modeling 1. Introduction Chronic obstructive pulmonary disease (COPD) is a re- spiratory condition which results in severe limitations in daily activities and quality of life. Given the nonreversible nature of COPD, the main goal of treatment is to maximize a person’s ability to function and maintain high levels of well-being [1e3]. As a result, health-related quality of life (HRQL) is increasingly becoming a part of the evaluation profile for interventions, particularly for those interventions involving health-services delivery. Pulmonary rehabilitation is a central component of clin- ical care and focuses on the multiple needs of patients with COPD. It includes physical rehabilitation and patient self- management support aimed at teaching patients skills needed to carry out medical regimens specific to the dis- ease, guide health behavior change, and provide emotional support for patients to control their disease and live func- tional lives [4e6]. Self-management programs teach patients new strategies to help them cope and adapt to their condition and often in- volves interacting with others who may be better or worse off than themselves. As a result, individuals may be expe- riencing a response shift defined as changes in internal stan- dards, conceptualization, and values in relation to the domains of HRQL [7,8]. In fact, response shift is often a de- sired effect of self-management programs. * Corresponding author. Faculty of Medicine, School of Physical and Occupational Therapy, 3654 Prom Sir-William-Osler, Montreal, Qu ebec H3G 1Y5, Canada. Tel: þ514-398-4400 ext. 00531; fax: þ514-398-6360. E-mail address: sara.ahmed@mail.mcgill.ca (S. Ahmed). 0895-4356/09/$ e see front matter Ó 2009 Elsevier Inc. All rights reserved. doi: 10.1016/j.jclinepi.2009.03.015 Journal of Clinical Epidemiology 62 (2009) 1165e1172