Summary
The 20-Item Short Form Health Survey (SF-20) was developed for the Medical Outcomes Study (MOS), a multi-year study of patients with chronic conditions. The resulting short-form survey instrument provides a solution to the problem faced by many investigators who must restrict survey length. The instrument was designed to reduce respondent burden while achieving minimum standards of precision for purposes of group comparisons involving multiple health dimensions.Description of the 20-Item Short-Form SurveyPhysical FunctioningSix items were selected to assess physical functioning, a dimension measured in the HIE by aggregating twenty items measuring physical limitations and capacities, mobility, and self- care (Stewart, Ware, and Brook, 1978; Stewart, Ware, and Brook, 1982.). The goal was to approximate as closely as possible the 6-level scale constructed in the HIE. Response choices and item wording were modified from the HIE version to capture better specific limitations of interest, to describe more accurately the scale level defined by each item, and to facilitate oral administration. One new item (moderate level of limitation in physical functioning) was added to fill a gap in the HIE scale.Role FunctioningTwo items were selected to measure limitations in role functioning due to poor health. These are the two best items from the 3-item HIE role functioning scale (Stewart, Ware, and Brook, 1978, 1981, 1982).Social FunctioningSocial functioning is defined as the ability to develop, maintain, and nurture major social relationships. The single social functioning survey item focuses on whether the respondent's health has limited social activities.Mental HealthGeneral mental health was assessed using five items derived empirically from the HIE Mental Health Inventory (MHI). This set is the best 5-item predictor of the summary score based on the full 38-item MHI (Davies, Sherbourne, Peterson, and Ware, 1988). The set represents the four major mental health dimensions (anxiety, depression, loss of behavioral-emotional control, and psychological well- being) as confirmed in factor-analytic studies of the MHI (Veit and Ware, 1983). These five items correlated 0.92 with the MHI total score in the HIE sample used to derive the short-form scale. On cross-validation using another HIE sample, the scale correlated 0.92 with the MHI total score (Davies, Sherbourne, Peterson, and Ware, 1988).Current Health PerceptionsThe 22-item Health Perceptions Questionnaire (HPQ) (Davies and Ware, 1981; Ware and Karmos, 1976; Ware, 1976) included six subscales that are substantially intercorrelated. The Current Health subscale was the most reliable and empirically valid of these (Davies and Ware, 1981). That subscale also best represents the overall HPQ concept, accounting for the largest amount of variance common to the HPQ subscales. For these reasons, four items were selected from the Current Health subscale (Davies and Ware, 1981). These items had high correlations with the Current Health subscale, had substantial and roughly equal correlations with other physical and mental health measures, and achieved the balance between favorably and unfavorably worded items necessary to control for acquiescent and opposition response sets.PainThe survey includes one measure of pain that asks respondents to rate pain on a scale from none to very severe.Scale ScoringConsistent with previous studies, limitations in physical and role functioning were counted regardless of duration and were scored to reflect the number of limitations present (Stewart et al. 1981; Stewart et al., 1982) Scores were reversed so that a high value indicated better functioning. Mental health scales were scored by summing the item responses, after reversing the scoring of some items, so that a high score indicated better health. Before combining items in the health perceptions scale, the response choices of the overall health item (item 1) were recoded to better reflect the unequal intervals of the item. The single-item measures were scored so that high scores indicated better social functioning and more pain. Finally, for all measures, scores were transformed linearly to 0-100 scales, with 0 and 100 assigned to the lowest and highest possible scores, respectively.Reliability and ValiditySupport for the reliability and construct validity of the SF-20 is provided in previously published documents (Stewart et al., 1988, Ware et al., 1992).Respondent BurdenSelf-administration requires approximately three minutes for most respondents. Administering the survey over the telephone requires about three or four minutes. These administration times represent a reduction in respondent burden of approximately ninety percent relative to the full-length versions from which the scales were derived.Survey StructureThe SF-20 is organized into six health dimensions:DimensionItemsQuestion(s)Physical Functioning6Q2a–fRole Functioning2Q4–5Social Functioning1Q6Mental Health5Q7–11Current Health Perceptions5Q1, Q12a–dPain1Q3Answer FormatsThe SF-20 uses three types of response scales:3-point scale (Physical Functioning, Role Functioning)Limited for more than 3 months / Limited for 3 months or less / Not limited at allYes, for more than 3 months / Yes, for 3 months or less / No5- or 6-point scale (Pain, Mental Health, Social Functioning)Ranges from None to Very Severe (Pain)Ranges from All of the time to None of the time (Mental Health, Social Functioning)5-point true/false scale (Health Perceptions)Definitely true / Mostly true / Not sure / Mostly false / Definitely falseScoringEach of the six dimensions is scored separately as an average. There is no single overall total score.General Rules:All scales are transformed to a 0–100 range, where 0 = worst possible health and 100 = best possible healthA higher score always indicates better health on every dimensionSome items are reverse-scored before calculation so that all items point in the same directionResourcesSurvey Instrument: https://www.rand.org/health/surveys/mos/20-item-short-form/survey-instrument.htmlScoring & Description: https://www.rand.org/health/surveys/mos/20-item-short-form/more.htmlBibliography for the RAND Medical Outcomes Study 20-Item Short Form Survey (SF-20)Davies, A. R., Sherbourne, C. D., Peterson, J. R. and Ware, J. E. 1988. Scoring manual: Adult health status and patient satisfaction measures used in RAND's Health Insurance Experiment. N-2190-HHS. Santa Monica, Calif.: RAND Corporation.Davies, A. R., and Ware, J. E. 1981. Measuring health perceptions in the Health Insurance Experiment. R-2711-HHS. Santa Monica, Calif.: RAND Corporation.Stewart, A. L., Sherbourne, C., Hays, R. D., et al. 1992. Measuring Functioning and Well-Being: The Medical Outcomes Study approach. Durham, NC: Duke University Press.Stewart, A. L., Ware, J. E., and Brook, R. H. 1978. Conceptualization and measurement of health for adults in the Health Insurance Study: Vol. 2, Physical health in terms of functioning. R-1987/2-HEW. Santa Monica, Calif.: RAND Corporation.Stewart, A. L., Ware, J. E., and Brook, R. H. 1981. "Advances in the measurement of functional status: Construction of aggregate indexes." Medical Care 19:473-88.Stewart, A. L., Ware, J. E., and Brook, R. H. 1982. Construction and scoring of aggregate functional status measures: Vol. 1. R2551-1-HHS. Santa Monica, Calif.: RAND Corporation.Stewart, A. L., Hays, R. D., & Ware, J. E. (1988). The MOS short-form general health survey: Reliability and validity in a patient population. Medical Care, 26, 724-735.Veit, C. T., & Ware, J. E. 1983. "The structure of psychological distress and well-being in general populations". Journal of Consulting and Clinical Psychology, 51, 730-742.Ware, J. E. 1976. "Scales for measuring general health perceptions." Health Services Research 11:396-415.Ware, J. E. 1987. "Standards for validating health measures: Definition and content." Journal of Chronic Disease 40:473-80.Ware, J. E., and Karmos, A. H. 1976. "Scales for measuring general health perceptions." Health Services Research 11:396-415.Ware, J. E., Sherbourne, C. D., & Davies, A. R. (1992). Developing and testing the MOS 20-item short-form health survey: A general population application. In A. L. Stewart & J. E. Ware (eds.), Measuring functioning and well-being: The Medical Outcomes Study approach (pp. 277-290), Durham, NC: Duke University Press.