THE MOS 36-ITEM SHORT-FORM HEALTH SURVEY (SF-36) .3. TESTS OF DATA QUALITY, SCALING ASSUMPTIONS, AND RELIABILITY ACROSS DIVERSE PATIENT GROUPS

The widespread use of standardized health surveys is predicated on the largely untested assumption that scales constructed from those survey s will satisfy minimum psychometric requirements across diverse popula tion groups. Data from the Medical Outcomes Study (MOS) were used to e valuate data completeness and quality, test scaling assumptions, and e stimate internal-consistency reliability for the eight scales construc ted from the MOS SF-36 Health Survey. Analyses were conducted among 3, 445 patients and were replicated across 24 subgroups differing in soci odemographic characteristics, diagnosis, and disease severity. For eac h scale, item-completion rates were high across all groups (88% to 95% ), but tended to be somewhat lower among the elderly, those with less than a high school education, and those in poverty. On average, survey s were complete enough to compute scale scores for more than 96% of th e sample. Across patient groups, all scales passed tests for item-inte rnal consistency (97% passed) and item-discriminant validity (99% pass ed). Reliability coefficients ranged from a low of 0.65 to a high of 0 .94 across scales (median = 0.85) and varied somewhat across patient s ubgroups. Floor effects were negligible except for the two role disabi lity scales. Noteworthy ceiling effects were observed for both role di sability stales and the social functioning scale. These findings suppo rt the use of the SF-36 survey across the diverse populations studied and identify population groups in which use of standardized health sta tus measures may or may not be problematic.