The Diabetes Treatment Satisfaction Questionnaire change version (DTSQc) evaluated in insulin glargine trials shows greater responsiveness to improvements than the original DTSQ

BACKGROUND: The results of using status measures to identify any changes in treatment satisfaction strongly suggest a need for specific change instruments designed to overcome the ceiling effects frequently observed at baseline. Status measures may leave little room to show improvement in situations where baseline ceiling effects are observed. A change version of the DTSQ (DTSQc) is compared here with the original status (now called DTSQs) version to test the instruments' comparative ability to demonstrate change. METHODS: Two multinational, openlabel, randomised-controlled trials (one for patients with type 1 diabetes, the other for type 2) compared new, longer-acting insulin glargine with standard NPH basal insulin. The DTSQs was completed at baseline and the DTSQs and DTSQc at final visit by 351 English- and German-speaking patients. DTSQc scores were compared with change from baseline for the DTSQs, using 3-way analysis of variance, to examine Questionnaire, Treatment and Ceiling effects (i.e. baseline scores at/near ceiling). RESULTS AND DISCUSSION: Significant Questionnaire effects and a Questionnaire × Ceiling interaction (p < 0.001) in both trial datasets showed that the DTSQc detected more improvement in Treatment Satisfaction than the DTSQs, especially when patients had DTSQs scores at/near ceiling at baseline. Additionally, significant Treatment effects favouring insulin glargine (p < 0.001) and a Treatment × Questionnaire interaction (p < 0.019), with the DTSQc showing more benefits, were found in the type 1 trial. Results for Perceived Hyper- and Hypoglycaemia also demonstrated important differences between the questionnaires in the detection of treatment effects. Tests of effect sizes showed these differences in response to change to be significantly in favour of the DTSQc. CONCLUSION: The DTSQc, used in conjunction with the DTSQs, overcomes the problem of ceiling effects encountered when only the status measure is used and provides a means for new treatments to show greater value than is possible with the DTSQs alone.