ORIGINAL ARTICLE Short-form Zarit Caregiver Burden Interviews were valid in advanced conditions Irene J. Higginson a, * , Wei Gao a , Diana Jackson a , Joanna Murray b , Richard Harding a a King’s College London, Department of Palliative Care, Policy and Rehabilitation, School of Medicine at Guy’s, King’s College and St Thomas’ Hospitals, London, United Kingdom b King’s College London, Health Service and Population Research Department, Institute of Psychiatry, David Goldberg Centre, London, United Kingdom Accepted 3 June 2009 Abstract Objectives: To assess six short-form versions of Zarit Burden Interview (ZBI-12, ZBI-8, ZBI-7, ZBI-6, ZBI-4, and ZBI-1) among three caregiving populations. Study Design and Setting: Secondary analysis of carers’ surveys in advanced cancer (n 5 105), dementia (n 5 131), and acquired brain injury (n 5 215). All completed demographic information and the ZBI-22 were used. Validity was assessed by Spearman correlations and internal consistency using Cronbach’s alpha. Overall discrimination ability was evaluated using the area under the receiver operating characteristic curve (AUC). Results: All short-form versions, except the ZBI-1 in advanced cancer (rho 5 0.63), displayed good correlations (rho 5 0.74e0.97) with the ZBI-22. Cronbach’s alphas suggested high internal consistency (range: 0.69e0.89) even for the ZBI-4. Discriminative ability was good for all short forms (AUC range: 0.90e0.99); the best AUC was for ZBI-12 (0.99; 95% confidence interval [CI]: 0.98e0.99) and the second best for ZBI-7 (0.98; 95% CI: 0.96e0.98) and ZBI-6 (0.98; 95% CI: 0.97e0.99). Conclusions: All six short-form ZBI havevery good validity, internal consistency, and discriminative ability. ZBI-12 is endorsed as the best short-form version; ZBI-7 and ZBI-6 show almost equal properties and are suitable when a fewer-question version is needed. ZBI-4 and ZBI-1 are suitable for screening, but ZBI-1 may be less valid in cancer. Ó 2010 Elsevier Inc. All rights reserved. Keywords: Carer; Outcome; Palliative; Burden; Aging; Validity 1. Background Informal carers are the primary resource for patient care and are known to have high needs for support and psycho- logical morbidity [1e4]. Although there are many sug- gested interventions seeking to improve their overall well-being, there is little evaluative research into the efficacy of such interventions [5,6]. Measurement of appro- priate carer outcomes is essential for such studies. Although there are many measures to assess caregiver burden, strain, well-being, or other outcomes in specific disease, such as stroke or mental illness [7,8], there are fewer measures targeted for the carers of patients with advanced disease. Mularski et al. in a major systematic review of measures for use toward the end of life for the National Institute of Health (USA) highlighted ‘‘significant gaps’’ in measuring caregiver outcomes, identifying only two measures in their literature search of 24,423 citations [9]. Caregiver burden is closely aligned to the goals of many interventions and is associated with negative health out- comes in carers of people with common conditions, such as dementia, stroke, and cancer [8,10,11]. Moreover, per- ceived burden had been shown to predict anxiety and depression in carers of patients with these conditions [12e14]. Caregiver burden had been defined as a context- specific negative affective outcome, occurring as a result of perceived inability to contend with role demands [15]. There is general agreement that caregiver burden is a multi- dimensional concept affected by objective elements related to the nature and time of the practical tasks undertaken by carers and subjective elements arising from the perceived emotional, social, and relationship stresses that can accom- pany this role [8,16]. Therefore, it would seem appropriate to measure caregiver burden as an outcome in advanced disease. Competing interests: None. * Corresponding author. Department of Palliative Care, Policy and Re- habilitation, School of Medicine at Guy’s, King’s College and St Thomas’ Hospitals, King’s College London, Weston Education Centre, 3rd Floor, Cutcombe Road, Denmark Hill, London SE5 9RJ, United Kingdom. Tel.: þ44-0-20-7848-5516; fax: þ44-0-20-7848-5517. E-mail address: irene.higginson@kcl.ac.uk (I.J. Higginson). 0895-4356/10/$ e see front matter Ó 2010 Elsevier Inc. All rights reserved. doi: 10.1016/j.jclinepi.2009.06.014 Journal of Clinical Epidemiology 63 (2010) 535e542