Validation of the Thai version of the Duke Activity Status Index in patients with a previous myocardial infarction

Background: The Duke Activity Status Index is a widely used instrument for measuring functional status in patients with cardiovascular disease. However, items and subscales on this instrument have not been validated for Thai patients with a previous myocardial infarction (MI) Objective: To test the reliability and validity of the Thai version of the Duke Activity Status Index (DASI-T) in Thai patients with a previous MI using a cross-sectional study design. Methods: The DASI-T was translated using forward and backward translation methods and administered to 100 MI patients from outpatient departments of two general hospitals in Thailand. Internal consistency was determined to test reliability. Two criterion measures (i.e. Canadian Cardiovascular Society (CCS) classification, SF-36 physical functioning subscale) were used to test the concurrent validity of the DASI-T. Age group and CCS classification were used to determine known-groups validity of the DASI-T. Results: Cronbach's a for the DASI-T total score was 0.76. No ceiling or floor effect was detected for the DASI-T total score. DASI-T total score was significantly correlated with the CCS classification (r=-0.68,P < 0.01) and SF-36 physical functioning subscale (r = 0.79, P < 0.01). DASI-T total scores could differentiate MI patients based on age (P = 0.040) or CCS classification (P = 0.000). Conclusion: The DASI-T is a potentially reliable and valid instrument with which to assess functional status in MI patients and is also useful to evaluate a treatment effect and be a guideline for clinical purposes (i.e. exercise prescription, risk stratification).