Psychometric properties and responsiveness of the Turkish version of the Diabetes Treatment Satisfaction Questionnaire (s) on a sample of diabetics of three consecutive monitoring periods

The aim of this study is to test the psychometric properties and the responsiveness of the original (status) version of Turkish DTSQ. The study sample included 88 patients with diabetes mellitus who were evaluated in three consecutive time points. The first data collection time point was during their initial contact to the clinic, and the two following (3rd month and 6th month) were during the monitoring visits to the Celal Bayar University Endocrinology Department in 2007. After the adaptation of the DTSQ to Turkish language by following standard procedures, this instrument was applied to the patients along with WBQ-12 and World Health Organization Quality of Life Measure (WHOQOL-Bref). The reliability of the DTSQ was evaluated by running internal consistency analysis (Cronbach Alpha) and item analysis. Construct validity of the instrument was evaluated by various tests such as Principal Components analysis, Confirmatory Factor Analysis, Concurrent validity and “Known Groups” comparisons. Finally the sensitivity (responsiveness to change) of the DTSQ scores to the changes of the metabolic conditions were assessed. 50.0% of the participants were male with a mean age of 51.1 ± 11.4 (min 22, max 78). Majority of them had type 2 diabetes (86.4%) and 72.7% of these patients had at least one co-morbid chronic conditions. While 53.4% of the patients had been treated by insulin the remaining 46.6% had been taking oral anti-diabetic agents. The results revealed satisfactory alpha values for DTSQ (α > 0.70). All of the three metabolic measures (i.e., FBG, PBG, and HbA1c) had significant correlations with the DTSQ scores. The criterion and construct validity of the scale were found to be very satisfactory. The Turkish version of the DTSQ showed acceptable fit indices (RMSEA = 0.03, CFI > 0.90) with the original (hypothetic) construct. Almost all of the sub-dimensions of the WBQ and WHOQOL were correlated with the DTSQ as expected, indicating a good concurrent validity. DTSQ status version was found to be a reliable and valid instrument for the assessment of treatment satisfaction in Turkish diabetes mellitus patients.