The eight-item modified Medical Outcomes Study Social Support Survey: psychometric evaluation showed excellent performance.

OBJECTIVE Evaluation and validation of the psychometric properties of the eight-item modified Medical Outcomes Study Social Support Survey (mMOS-SS). STUDY DESIGN AND SETTING Secondary analyses of data from three populations: Boston breast cancer study (N=660), Los Angeles breast cancer study (N=864), and Medical Outcomes Study (N=1,717). The psychometric evaluation of the eight-item mMOS-SS compared performance across populations and with the original 19-item Medical Outcomes Study Social Support Survey (MOS-SS). Internal reliability, factor structure, construct validity, and discriminant validity were evaluated using Cronbach's alpha, principal factor analysis (PFA), and confirmatory factor analysis (CFA), Spearman and Pearson correlation, t-test and Wilcoxon rank sum tests. RESULTS mMOS-SS internal reliability was excellent in all three populations. PFA factor loadings were similar across populations; one factor >0.6, well-discriminated two factor (instrumental/emotional social support four items each) >0.5. CFA with a priori two-factor structure yielded consistently adequate model fit (root mean squared errors of approximation 0.054-0.074). mMOS-SS construct and discriminant validity were similar across populations and comparable to MOS-SS. Psychometric properties held when restricted to women aged ≥ 65 years. CONCLUSION The psychometric properties of the eight-item mMOS-SS were excellent and similar to those of the original 19-item instrument. Results support the use of briefer mMOS-SS instrument; better suited to multidimensional geriatric assessments and specifically in older women with breast cancer.