The WHOQOL-100 has good psychometric properties in breast cancer patients Brenda L. Den Oudsten a, * , Guus L. Van Heck a,b , Alida F.W. Van der Steeg c , Jan A. Roukema a,d , Jolanda De Vries a a CoRPSdCenterof Research on Psychology in Somatic Diseases, Department of Medical Psychology, Tilburg University, Tilburg b Scientific Centre for Transformation in Care and Welfare, Tilburg University, Tilburg c Pediatric Surgical Centre of Amsterdam, Emma Children’s Hospital and VU Medical Centre, Amsterdam d Department of Surgery, St. Elisabeth Hospital, Tilburg, The Netherlands Accepted 26 March 2008 Abstract Objective: This prospective follow-up study examines the psychometric properties of the World Health Organization Quality of Life assessment instrument (WHOQOL-100) for assessing quality of life in women suspected of having breast cancer and disease-free breast cancer survivors. Study Design and Setting: The WHOQOL-100 was tested at five points in time in women with a palpable lump in the breast or an abnormality on a screening mammography (N 5 356) and breast cancer survivors (N 5 140). Furthermore, all participants completed mea- sures of anxiety (State Trait Anxiety Inventory) and depression (Center for Epidemiologic Studies Depression scale). Moreover, women who were diagnosed with breast cancer also completed the EORTC-QLQ-BR-23 at time points 2e5. Reliability (internal consistency; test- eretest reliability) and construct validity were tested. Results: Confirmatory factor analyses on the WHOQOL-100 items showed a good fit with models reflecting six factors (physical health, psychological health, level of independence, social relationships, environment, spirituality/religion/personal beliefs) or four factors (physical health, psychological health, social relationships, environment). Internal consistency was adequate. Testeretest correlations were high. The WHOQOL-100 correlated highly with related constructs and showed low correlations with unrelated constructs. Conclusion: The WHOQOL-100 is a reliable and valid instrument for measuring QOL in women suspected of having breast cancer and disease-free breast cancer survivors. Ó 2008 Elsevier Inc. All rights reserved. Keywords: WHOQOL-100; Quality of life; Reliability; Validity; Breast cancer; Survivors 1. Introduction Breast cancer is the most common malignancy in women [1] and the most frequent cause of death in women aged 35e60 years in Europe [2]. In the Netherlands, one in every nine women will develop breast cancer before the age of 85 [3]. The prevalence of breast cancer increases with age from 3% to 4% at age 50e69 to 6% of women older than 70 [4]. Following a breast cancer diagnosis, up to 4 in 10 women is experiencing symptoms of anxiety and de- pression [5]. For this reason, and also due to the growing number of breast cancer survivors [6], it has become in- creasingly important to include in research not only medical endpoints (e.g., morbidity and mortality), but also patient-based outcome measures, such as quality of life (QOL). Therefore, the aim of this prospective follow-up study was to examine the psychometric properties of the World Health Organization Quality of Life assessment instrument (WHOQOL-100), a multidimensional QOL instrument. QOL has become a popular concept in research. How- ever, the debate on how to conceptualize QOL is still ongo- ing. Many different conceptualizations are covered by numerous instruments, for instance, the Short Form Health Surveye36 items (SF-36; [7]), and the EORTC Quality of Life Questionnairee30 items [8], and its complementary breast-cancer module (QLQ BR-23; [9]). Although a gold standard does not exist, the majority of the literature sup- ports the multidimensional aspect of QOL, in which QOL consists of at least a physical, an emotional, and a social domain [10]. Another commonly accepted characteristic * Corresponding author. CoRPS, Department of Medical Psychology, Tilburg University, P.O. Box 90153, 5000 LE Tilburg, The Netherlands. Tel.: þ31-134662940; fax: þ31-134662067. E-mail address: b.l.denoudsten@uvt.nl (B.L. Den Oudsten). 0895-4356/08/$ e see front matter Ó 2008 Elsevier Inc. All rights reserved. doi: 10.1016/j.jclinepi.2008.03.006 Journal of Clinical Epidemiology - (2008) - ARTICLE IN PRESS