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OBJECTIVE: This study aimed to test the validity of the 36-item Short-Form Health Survey (SF-36) scales and summaries in patients with severe functional somatic syndromes (FSS), such as fibromyalgia and irritable bowel syndrome. STUDY DESIGN AND SETTING: One hundred twenty patients with severe FSS enrolled in a randomized controlled trial filled in the SF-36 questionnaire. We tested for data quality, central scaling assumptions, and agreement with the conceptual model. RESULTS: Most SF-36 scales were found to be valid; however, three scales (role physical, role emotional, and general health) did not satisfy predefined criteria for construct validity, internal consistency, or targeting to the sample. The correlations between SF-36 scales differed considerably from those reported in the general population. As a consequence, the SF-36 summaries, physical component summary (PCS) and mental component summary (MCS), did not accurately reflect their underlying scales and were negatively correlated (r=-0.46, 95% CI [-0.60 to -0.31]). CONCLUSION: Although the SF-36 is a valuable instrument to assess perceived health in patients with severe FSS, there are problems with some of the scales and with the scoring procedure of the summaries. The SF-36 PCS may, therefore, not accurately measure the physical health status of these patients. Alternative summary measures are needed.

Original publication

DOI

10.1016/j.jclinepi.2011.03.012

Type

Journal article

Journal

J Clin Epidemiol

Publication Date

01/2012

Volume

65

Pages

30 - 41

Keywords

Adult, Algorithms, Female, Fibromyalgia, Health Surveys, Humans, Irritable Bowel Syndrome, Male, Outcome Assessment (Health Care), Quality of Life, Randomized Controlled Trials as Topic, Reproducibility of Results, Research Design, Sampling Studies, Self-Assessment, Severity of Illness Index, Sickness Impact Profile, Somatoform Disorders, Surveys and Questionnaires, Syndrome