Construct validity of the RAND-12 and Health Utilities Index Mark 2 and 3 in type 2 diabetes

Objective: To assess the cross-sectional construct validity of the RAND-12 and the Health Utilities Index Mark 2 (HUI2) and Mark 3 (HUI3) in type 2 diabetes. Methods: Parametric tests were used to test for differences in HRQL scores between known groups with type 2 diabetes, defined in terms of treatment intensity, duration of diabetes and glycemic control. Results: The PHC of the RAND-12 was significantly lower for individuals treated with insulin (40.28 +/- 10.97) than diet alone (45.18 +/- 12.02, p < 0.01), as was the MHC (42.83 +/- 10.75 vs. 46.87 +/- 10.89, p < 0.05). MHC (43.56 +/- 10.20 vs. 46.18 +/- 9.94, p < 0.05) and PHC (41.04 +/- 10.64 vs. 45.62 +/- 10.48, p < 0.001) were both lower for those with longer duration of diabetes. Overall HUI3 scores were lower in individuals above the median duration of diabetes (5.0 years) as compared to those with a shorter duration (0.60 +/- 0.29 vs. 0.67 +/- 0.29, p < 0.01) and for individuals whose diabetes was managed using insulin compared to diet alone (0.59 +/- 0.30 vs. 0.69 +/- 0.30, p < 0.05). Disease severity was associated with impairment on the ambulation, dexterity and pain attributes of the HUI3. Similar results were found for the HUI2. Overall HUI2 scores were highest for individuals managed with diet alone compared to those managed with insulin. Disease severity was associated with the mobility and self-care attributes of the HUI2. No relationship was found between any of the measures of HRQL and glycemic control. Conclusions: Scores for individuals presumed to have more severe or advanced disease were significantly lower for many comparisons using the RAND-12, HUI2 and HUI3. The results of this study contribute evidence of construct validity of the HUI2, HUI3 and RAND-12 in type 2 diabetes.