Objective: To assess the psychometric validity, reliability, responsiveness, and minimal important differences of the Diabetes Symptoms Checklist-Revised (DSC-R), a widely used patient-reported outcome measure of diabetes symptom distress.
Research design and methods: Psychometric validity of the DSC-R was assessed using blinded data from a large-scale trial of approximately 4000 type 2 diabetes patients. Confirmatory factorial analysis (CFA) and multitrait analysis were used to examine the construct validity of the structure of DSC-R. DSC-R internal consistency, discriminative validity, and responsiveness were also assessed. Distribution and anchor-based methods were used to estimate minimal important differences for DSC-R domains.
Results: Mean age of the sample was 56 years, 42% were female, 88% were Caucasian. Patients had a mean body mass index (BMI) of 32.2 and mean glucose-fasting level of 151.7 md/dl. CFA and multitrait analysis indicated that the scoring of the DSC-R has acceptable construct validity. Item-scale correlations ranged from 0.44 to 0.78. Cronbach's alpha coefficients ranged from 0.69 to 0.87. At baseline, DSC-R scores were higher among patients with higher BMI scores (P < 0.0001), supporting the discriminative validity of the DSC-R. Minimal important difference estimates ranged from 0.39 to 0.60 points when using distribution methods and from 0.00 to 0.33 when estimated using anchor-based methods.
Conclusions: The DSC-R demonstrated excellent psychometric properties when tested in a large-scale diabetes clinical trial. Responsiveness and test-retest reliability of the DSC-R warrant further evaluation.