The Psychometric Properties of General Adherence Scale in Chinese (GAS-C) in Patients with Type 2 Diabetes Using Insulin.

Purpose: Translate General Adherence Scale (GAS) into Chinese and test its psychometric properties in middle-aged and elderly type 2 diabetes (T2D) patients using insulin in the Han people of urban China.

Subjects And Methods: We translated the GAS into Chinese and established General Adherence Scale in Chinese (GAS-C). 136 T2D subjects were selected for testing GAS-C's reliability and validity, of which 100 study subjects were retested with GAS-C two weeks later. The other 200 T2D subjects were selected for performing Confirmatory Factor Analysis(CFA). The ceiling effect and floor effect of GAS-C data were checked.

Results: No data was lost in our research. In exploratory factor analysis(EFA), the Kaiser-Meyer-Olkin measure of sampling adequacy (KMO) =0.899, Bartlett's Test's χ=611.821 (df=10 p<0.001). The communalities of the items were between 0.740 and 0.862; The values of Measure of Sampling Adequacy (MSA) were between 0.883 and 0.945. All five items entered the factor analysis process. A common factor was extracted, and it could explain 81.403% of the total variance. CFA validated the.one-factor model was good fits with the data of GAS-C (Ratio of Chi-square to Degrees of Freedom (CMIN/DF)=2.032, Goodness of Fit Index (GFI) =0.981, Comparative Fit Index (CFI) =0.996, Tucker-Lewis Index (TLI) =0.992, Root Mean Square Residual (RMR) =0.011, Root Mean Square Error of Approximation (RMSEA) =0.072). Correlation analysis was performed between GAS-C and MMAS-8 to calculate the criterion-related validity (r=0.542 p<0.001). The internal consistency reliability α=0.942, Intraclass Correlation Coefficient (ICC)= 0.941 (95% CI 0.924-0.955). The correlation coefficient r of the test-retest reliability was 0.772 (p<0.001). Spearman-Brown coefficient of split-half was 0.939. There was no floor effect and ceiling effect on the data.

Conclusion: GAS-C has good reliability and validity. It can be used for general adherence studies of middle-aged and elderly type 2 diabetic patients using insulin in the Han people of Chinese cities.