Investigating the minimally important difference of the Diabetes Health Profile (DHP-18) and the EQ-5D and SF-6D in a UK diabetes mellitus population

Abstract

Objectives: It is important to know what patient reported outcome measure (PROM) scores relate to a meaningful change in health status across time. The aim of this study was to investigate the minimally important difference (MID) of the Diabetes Health Profile (DHP-18), EQ-5D and SF-6D in a Type 1 and Type 2 diabetes patient sample. Methods: A longitudinal dataset including a UK community sample of people with Type 1 and Type 2 diabetes was used for the analysis. A combination of anchor and distribution methods was used to investigate the MID. For the anchor based method, a global health change indicator was used if it correlated with the PROM scores at baseline and follow up. To calculate the anchor based MID, the change in PROM score for those reporting no change on the anchor was subtracted from those reporting small change. For the distribution based estimation, the 1 Standard Error of Measurement, 0.5 and 0.33 standard deviation methods were used. Results: The anchor was not correlated with the DHP-18 dimensions so was only used to estimate MID values for the EQ-5D and SF-6D. For the DHP-18, MID estimates for the Psychological Distress domain range from 6.99 to 10.59, the Barriers to Activity domain range from 6.48 to 9.89, and the Disinhibited Eating domain range from 7.52 to 11.39. The EQ-5D estimations range from 0.058 to 0.158, and the SF-6D estimations range from 0.038 to 0.081. The 0.5 SD and 1SEM estimations are of a similar magnitude across the three measures. Conclusions:This study has derived a range of values for each measure that may correspond to an important change in health status. The MID values may guide researchers who are using the measures as part of their assessment of both Type 1 and Type 2 patients with diabetes mellitus.