Psychometric properties of the Chinese version of the Perceived Therapeutic Efficacy Scale for type 2 diabetes

Background/Purpose: The purpose of this study was to test the psychometric properties of the Perceived Therapeutic Efficacy Scale (PTES) for type 2 diabetes with a Taiwanese sample. The mortality rate and health care cost of diabetes have dramatically increased in Taiwan, with many people with diabetes lacking the ability to control their disease appropriately. Addressing this problem requires enhancing self-efficacy towards self-management. Thus, there is a particular need for research into developing a diabetes-specific self-efficacy measurement instrument in Taiwan. Methods: This study was under-taken in two stages. Stage 1 consisted of forward and back translation of the PTES into Chinese and examination of content validity. Stage 2 established the validity and reliability of the Chinese version of PTES (C-PTES). A total of 230 people with type 2 diabetes aged 30 years or more from a diabetes outpatient clinic and taking oral medicine were recruited for psychometric testing. Results: Significant criterion-related validity was demonstrated between the C-PTES and the Summary of Diabetes Self-Care Activities scores (r=0.32; p < 0.01). Convergent validity was confirmed as the C-PTES converged well with the General Self-Efficacy Scale in measuring self-efficacy (r=0.42; p < 0.01); construct validity using factor analysis composed a single subscale. Internal consistency showed Cronbach's alpha was 0.95 and the test-retest reliability (Pearson's correction) was 0.79 (p<0.01) and a Bland-Altman plot showed that 97% of the subjects were within two standard deviations of the mean. Conclusion: The results of reliability and validity strengthen confidence in using the C-PTES. The C-PTES requires future studies to confirm the psychometric properties.