The Spirituality Index of Well-Being: a new instrument for health-related quality-of-life research.

PURPOSE Despite considerable interest in examining spirituality in health-related quality-of-life studies, there is a paucity of instruments that measure this construct. The objective of this study was to test a valid and reliable measure of spirituality that would be useful in patient populations. METHODS We conducted a multisite, cross-sectional survey using systematic sampling of adult outpatients at primary care clinic sites in the Kansas City metropolitan area (N = 523). We determined the instrument reliability (Cronbach's alpha, test-retest) and validity (confirmatory factor analysis, convergent and discriminant validation) of the Spirituality Index of Well-Being (SIWB). RESULTS The SIWB contains 12 items: 6 from a self-efficacy domain and 6 from a life scheme domain. Confirmatory factor analysis found the following fit indices: chi2 (54, n = 508) = 508.35, P < .001; Comparative Fit Index = .98; Tucker-Lewis Index = .97; root mean square error of approximation = .13. The index had the following reliability results: for the self-efficacy subscale, alpha = .86 and test-retest r = 0.77; for the life scheme subscale, alpha = .89 and test-retest r = 0.86; and for the total scale alpha = .91 and test-retest r = 0.79, showing very good reliability. The SIWB had significant and expected correlations with other quality-of-life instruments that measure well-being or spirituality: Zung Depression Scale (r = 0-.42, P < .001), General Well-Being Scale (r = 0.64, P < .001), and Spiritual Well-Being Scale (SWB) (r = 0.62, P < .001). There was a modest correlation between the religious well-being subscale of the SWB and the SIWB (r = 0.35, P < .001). CONCLUSIONS The Spirituality Index of Well-Being is a valid and reliable instrument that can be used in health-related quality-of-life studies.