Validity and responsiveness of Short Form 12-item survey in patients with back pain

Abstract Purpose of study: There is a growing recognition in the area of back pain research that evaluation of health-related quality of life (HRQL) is important for assessing the treatment effectiveness and for making clinical decisions. Numerous measures have been developed to assess HRQL. Among them, Short Form 12-item survey (SF-12) has become many back pain researchers' top choice, because this instrument is much shorter than many other HRQL measures and can significantly reduce the burden of respondents and the cost for data collection. Despite its widespread use, the validity and responsiveness of SF-12 in patients with back pain have not been well established. The purpose of this study is to evaluate the validity and responsiveness of SF-12 in patients with back pain. Methods used: Starting from January 1998, patients who consulted the Duke University Spine Center were asked to complete a comprehensive computerized survey questionnaire. The questionnaire included SF-12, Oswestry Back Disability Index and questions concerning patients' demographic characteristics, psychosocioeconomic status, medical history, present spine symptoms and the severity of back pain. A total of 2,520 patients who indicated in their first surveys that they had back pain were included in the validity study. Of these patients, 506 completed another survey in 3 to 6 months of follow-up and were used for assessing the responsiveness of SF-12. Only construct validity was evaluated, because content validity has been established, and the current lack of the “gold standard” for HRQL measure makes it difficult to determine the criteria validity. Construct validity was evaluated by assessing the correlation between the two summary scales of SF-12 and six other measures theoretically related or unrelated to these scales. of findings: Physical component summary of SF-12 (PSC-12) was significantly correlated with age, back pain, measures of overall well being and Oswestry Back Disability Index. Mental component summary of SF-12 (MCS-12) was significantly correlated with stress, depression, back pain, measures of overall well being and Oswestry Back Disability Index. Both PCS and MCS performed as expected without exception, demonstrating the construct validity of SF-12. The responsiveness of SF-12 was supported by several pieces of evidence. First, the changes in PCS-12 and MCS-12 were significantly correlated with the changes in back pain intensity. Second, for patients whose back pain improved, there was a significant increase in the follow-up PCS-12 and MCS-12 as compared with the baseline. Third, in the group whose back pain became improved or became worse, small to large effect size was obtained for PCS-12 or MCS-12. Relationship between findings and existing knowledge: To our knowledge, the current study is the first to evaluate the validity and responsiveness of SF-12 in patients with back pain. Overall Significance of findings: The current study demonstrated that SF-12 was a valid and responsive instrument for measuring health status or HRQL in patients with back pain. Given its brevity and the current findings, SF-12 may be considered as a useful outcome tool in the future back pain research. Disclosures: No disclosures. Conflict of interest: No conflicts.