Measuring disability in patients with chronic fatigue syndrome: reliability and validity of the Work and Social Adjustment Scale Matteo Cella a, b, ⁎, Michael Sharpe c , Trudie Chalder a a Institute of Psychiatry, King's College London, UK b Department of Clinical, Educational & Health Psychology, University College London, UK c Psychological Medicine Research, School of Molecular and Clinical Medicine, University of Edinburgh, UK abstract article info Article history: Received 23 September 2010 Received in revised form 2 February 2011 Accepted 24 February 2011 Keywords: Chronic fatigue syndrome Work and Social Adjustment Scale Disability Reliability Validity Background: Disability is a defining feature of chronic conditions, and it is an increasingly used measure of therapy effectiveness. The Work and Social Adjustment Scale (WSAS) is a simple and clear measure of disability. Although the scale is widely used, no study has yet investigated its psychometric properties in patients with chronic fatigue syndrome (CFS). Methods: Data from two samples of patients were used, one from a multicenter randomized controlled clinical trial of treatments for CFS (n =639) and the other from a clinic that specializes in CFS (n=384). All patients completed the WSAS as well as other measures. Results: Internal consistency and the Spearman–Brown split-half coefficient values indicated that the scale is reliable. CFS patients who had comorbid diagnoses of depression, anxiety or fibromyalgia had higher WSAS scores. High levels of disability were associated with high number of physical symptoms, severe fatigue, depression, anxiety, poor sleep quality and poor physical fitness, with correlation coefficients ranging between 0.41 and 0.11. Lower scores on the WSAS were modestly associated with better physical functioning as well as higher levels of physical capacity as assessed by a walking test. Sensitivity to change was evaluated in a subgroup of patients who had undergone a course of cognitive behavioral therapy. Disability significantly decreased after therapy and remained stable at follow-ups. Conclusion: The WSAS is a reliable and valid assessment tool for disability in patients with CFS. © 2011 Elsevier Inc. All rights reserved. Introduction The World Health Organization defines disability as an umbrella term covering impairments, activity limitations and participation restrictions. This definition describes impairment as a problem in body function or structure, activity limitation as a difficulty encoun- tered by an individual in executing a task or action and participation restriction as a problem experienced by an individual in involvement in life situations [1]. Temporary episodes of disability are generally accepted as part of an illness course, but when disability is long lasting, these can become less tolerable. Disability is increasingly perceived as an important index of recovery, and intervention studies often include measures of disability as primary outcomes along with symptom reduction [2,3]. Disability is a characteristic feature of chronic fatigue syndrome (CFS). Between 27% and 65% of CFS patients are reported not to be working, and less than a third of untreated patients are estimated to resume employment within 3 years after diagnosis [4,5]. However, occupational outcomes tend to improve substantially for CFS patients who receive treatment such as cognitive behavioral therapy and graded exercise therapy [6]. Impairment in social and relational activities is also often reported by CFS patients [7]. Social and relational limitations are also likely to contribute to the high prevalence of emotional problems such as anxiety and depression observed in CFS [8]. The Work and Social Adjustment Scale (WSAS) is a five-item scale that assesses an individual's ability to perform everyday activities including work, home management, family and relationship interac- tion and social and private leisure activities. Each of the five items is rated on a 9-point scale ranging from 0 (not at all a problem) to 8 (very severely impaired) so that total scores range between 0 and 40, with high scores denoting higher levels of disability. The scale was first introduced by Marks [9], but the first study evaluating its psychometric proprieties in psychiatric groups [i.e., obsessive- compulsive disorder (OCD) and depression] was conducted by Mundt et al. [10]. These authors found that the WSAS had good internal consistency (i.e., Cronbach's α ranging between .70 and .90) and that it positively correlated with depressive symptom severity in de- pressed individuals as well as with obsessive-compulsive symptom Journal of Psychosomatic Research 71 (2011) 124–128 ⁎ Corresponding author. King's College London, Institute of Psychiatry, Department of Psychological Medicine, Weston Education Centre, Cutcombe Rd, SE5 9RJ London, UK. Tel.: +44 020 322 83191. E-mail address: matteo.cella@kcl.ac.uk (M. Cella). 0022-3999/$ – see front matter © 2011 Elsevier Inc. All rights reserved. doi:10.1016/j.jpsychores.2011.02.009 Contents lists available at ScienceDirect Journal of Psychosomatic Research