Assessment of the SF-36 version 2 in the United Kingdom

Objectives—To introduce the UK SF36 Version II (SF36-II), and to (a) gain population norms for the UK SF36-II in a large community sample as well as to explore the instrument’s internal consistency reliability and construct validity, and (b) to derive the Physical Component Summary (PCS) and Mental Component Summary (MCS) algorithms for the UK SF36-II. Design—Postal survey using a questionnaire booklet, containing the SF-36-II and questions on demographics and long term illness. Setting—The sample was drawn from General Practitioner Records held by the Health Authorities for Berkshire, Buckinghamshire, Northamptonshire, and Oxfordshire. Sample—The questionnaire was sent to 13 800 randomly selected subjects between the ages of 18–64 inclusive. Outcome measures—Scores for the eight dimensions of the UK SF36-II and the PCS and MCS summary scores. Results—The survey achieved a response rate of 64.4% (n=8889). Internal consistency of the diVerent dimensions of the questionnaire were found to be high. Normative data for the SF-36 are reported, broken down by age and sex, and social class. Factor analysis of the eight domains produced a two factor solution and provided weights for the UK SF36-II. Conclusion—The SF36-II domains were shown to have improved reliability over the previous version of the UK SF36. Furthermore, enhancements to wording and response categories reduces the extent of floor and ceiling eVects in the role performance dimensions. These advances are likely to lead to better precision as well as greater responsiveness in longitudinal studies. (J Epidemiol Community Health 1999;53:46–50) The SF-36 is a generic measure of health status, providing scores on eight areas of functioning and well being as well as two broad areas of subjective well being, namely physical health and mental health. 3 Data from the SF-36 have been suggested as appropriate for the evaluation of a wide variety of medical interventions. The measure has been widely adopted around the world and over 300 articles were published between 1988–95 that included data gained from the SF-36. It has been translated into 40 languages, including English, German, French, Polish, Swedish, Spanish, Icelandic, Japanese, and Portugese. User manuals for the questionnaire have been produced by the developers in the USA and also in the UK. 7 However, despite the widespread use of the measure criticism has been forthcoming concerning the layout and wording of some of the items. Consequently, the developers have produced a modified instrument, the SF-36 Version 2 (SF36-II), which is a direct descendent of the SF-36 Developmental Form and the SF-36 Mark 1 Standard Form. This paper introduces the UK SF36-II and assesses the internal consistency reliability and construct validity of the measure. It provides normative data, from a large scale social survey, the Third Oxford Health and Lifestyles Survey (OHLS-III), for the measure and outlines the derivation of the Physical Component Summary Score (PCS) and the Mental Health Component Summary Score (MCS) for the SF36-II. Methods The SF-36 is a 36 item questionnaire that measures eight multi-item dimensions of health: physical functioning (10 items) social functioning (2 items) role limitations due to physical problems (4 items), role limitations due to emotional problems (3 items), mental health (5 items), energy/vitality (4 items), pain (2 items), and general health perception (5 items). There is a further unscaled single item asking respondents about health change over the past year. For each dimension item scores are coded, summed, and transformed on to a scale from 0 (worst possible health state measured by the questionnaire) to 100 (best possible health state). Two standardised summary scores can also be calculated from the SF-36; the physical component summary (PCS) and the mental health component summary (MCS). Version 2.0 of the SF-36 Health Survey is a product of eight years of research and the experience documented in a wide variety of publications. Relative to the standard SF-36 improvements in the content and layout of Version 2.0 include: improvements in some instructions and questions to make the wording less ambiguous, most importantly the SF-36 has been accused of containing an item with a double negative, and this item has been reworded; greater comparability with translations widely used in the US and in developed countries; five level response sets in place of dichotomous response choices for seven items in the two role functioning scales. Minor modifications to the wording of six items on the SF-36 have been made to make it acceptable in the British context. These changes have been endorsed by the SF-36 developers. Version 2.0 includes algorithms for J Epidemiol Community Health 1999;53:46–50 46 Health Services Research Unit, University of Oxford, Institute of Health Sciences, Headington, Oxford OX3 7LF