Using the 12‐item General Health Questionnaire to screen psychological distress from survivorship to end‐of‐life care: dimensionality and item quality Wei Gao 1 , Daniel Stark 2 , Michael I. Bennett 3 , Richard J. Siegert 1 , Scott Murray 4 and Irene J. Higginson 1 * 1 Cicely Saunders Institute, Department of Palliative Care, Policy and Rehabilitation, School of Medicine, King’s College London, King’s Healthcare Partners, London, UK 2 St James’s Institute of Oncology, St James’s University Hospital, Leeds, UK 3 International Observatory on End of Life Care, School of Health and Medicine, Lancaster University, Lancaster, UK 4 Primary Palliative Care Research Group, Centre for Population Health Sciences: General Practice Teviot Place, University of Edinburgh, Edinburgh, UK *Correspondence to: Cicely Saunders Institute, Department of Palliative Care, Policy and Rehabilitation, School of Medicine, King’s College London, Bessemer Road, London SE5 9PJ, UK. E‐ mail: irene.higginson@kcl.ac.uk Received: 22 July 2010 Revised: 25 March 2011 Accepted: 28 March 2011 Abstract Objectives: This study aimed (i) to determine the factor structure of the 12‐item General Health Questionnaire (GHQ‐12) across the cancer trajectory represented by samples from three cancer care settings and (ii) to appraise the item misfit and differential item functioning (DIF) of the GHQ‐12. Data and methods: Data were from cancer outpatient (n = 200), general community (n = 364) and palliative care (n = 150) settings. The factor structure was tested using exploratory factor analysis followed by confirmatory factor analysis. The factors were assessed for correlation using Spearman’s ρ. The analyses were run separately for standard GHQ, Likert, modified Likert and chronic GHQ scoring and for the individual cancer settings. The best scoring method within the cancer setting was determined by Akaike’s information criterion (AIC). Item misfit (mean square, MNSQ; standardised z‐ score, ZSTD) and DIF were assessed using the Rasch model. Results: The best scoring method was the chronic GHQ for the cancer outpatient (AIC = -45.8), modified Likert for the general community (AIC = 9.6) and standard GHQ for the palliative care (AIC = -43.0). The GHQ‐12 displayed a correlated two‐factor structure (‘social dysfunction’ and ‘distress’); Spearman ρ values were 0.69, 0.82 and 0.88 in the cancer outpatient, the general community and the palliative care, respectively. One item in the palliative care indicated misfit (MNSQ = 1.62, ZSTD = 3.0). Five items in the cancer outpatient showed DIF by gender and age. Two items in the palliative care showed DIF by gender. Conclusions: The GHQ‐12 was more problematic (less clear factor structure and evidence of item bias) for newly diagnosed patients, less problematic for patients approaching end‐of‐life and satisfactory for patients between those times. Copyright © 2011 John Wiley & Sons, Ltd. Keywords: cancer; oncology; General Health Questionnaire; psychometric properties; end‐of‐life care; surviorship Background Cancer patients are at increased risk of developing anxiety and depression, which can occur at any time from diagnosis and decrease their quality of life and effective delivery of care [1–6]. However, it is often under‐recognised and under‐treated [7]. Psycholog- ical interventions have been shown to be beneficial in cancer patients, even at advanced stages [8–10]. Therefore, effective screening for psychological disorders is warranted. Moreover, cohort and inter- vention studies in the management of symptoms, including psychological problems, are urgently need- ed in people living with cancer [11]. Longitudinal and complex intervention studies will be more efficient if supported by an empirical understanding of measure- ment properties of patient‐reported outcome measures at different points in the history of the cancer. The 12‐item General Health Questionnaire (GHQ‐ 12), a brief self‐administered measure, has been used in various settings for screening psychological disorders [12–15]. It consists of six ‘positively phrased’ (PP) and six ‘negatively phrased’ (NP) items [16]. A total GHQ score is generated by combining all the items to represent the overall level of psychological distress. The GHQ‐12 was designed as a unidimensional measure, but two‐factor and three‐factor structures have frequently been reported [17–21]. If the GHQ‐12 is multidimensional, the total score may not be valid, although it could be func- tionally similar when all dimensions are strongly correlated. In a sample of 120 psychiatric outpatients with anxiety disorders and/or psychological disor- ders, Gao et al. found high correlations between three dimensions and proposed that it is acceptable to use this instrument as a one‐dimensional measure [21]. Copyright © 2011 John Wiley & Sons, Ltd. Psycho‐ Oncology Psycho‐ Oncology (2011) Published online in Wiley Online Library (wileyonlinelibrary.com). DOI: 10.1002/pon.1989