Development and validation of the insulin treatment appraisal scale (ITAS) in patients with type 2 diabetes

BACKGROUND: Timely initiation of insulin therapy in type 2 diabetes is important to achieve metabolic control but can be hindered by negative perceptions of patients regarding insulin treatment. To assess the appraisal of insulin therapy of persons with type 2 diabetes, we developed the insulin treatment appraisal scale (ITAS) and tested its reliability and validity in insulin treated type 2 diabetes patients. METHODS: A sample of 282 patients with type 2 diabetes form the United States (US) completed the ITAS, the WHO-5 Well-being index (WHO-5) and the Problem Areas in Diabetes (PAID) Survey. Exploratory factor analysis (EFA), internal consistency (Cronbach's alpha) and item-total correlations were determined to test the reliability of the instrument. Concurrent validity was examined by calculating Pearson correlation coefficients between the different measures. Discriminant validity was examined by comparing ITAS scores of insulin naive and insulin using patients. RESULTS: EFA suggested a two-factor structure, separating positively worded and negatively worded items. Cronbach's alpha was 0.90 for the negative appraisal scale and 0.68 for the positive appraisal scale. Yet, Cronbach's alpha of the total 20-item scale was 0.89, suggesting high homogeneity and allowing for calculation of an overall score. Item-total correlations were in the range of 0.46–0.74 for the negative and 0.34 – 0.53 for the positive appraisal scale. The item pertaining to weight gain, as part of the negative appraisal subscale, showed low communality and deserves further testing. Concurrent validity was confirmed with low to moderate correlations in the expected direction between ITAS and WHO-5 and PAID. Discriminant validity was confirmed by the fact that patients using insulin had significantly less negative appraisals than insulin naive patients. CONCLUSION: The ITAS is a brief, psychometrically sound instrument that can be used in insulin naive and insulin-treated patients to assess positive and negative perceptions regarding insulin treatment and changes therein.