Problems with the performance of the SF-36 among people with type 2 diabetes in general practice

Objective: To validate the short form-36 (SF-36) among people with type 2 diabetes in general practice, and to make comparisons with the Audit of Diabetis Dependent Quality of Life (ADDQoL). Design: Postal survey with one reminder. Setting: Four general practices. Patients: One hundred and eighty-four eligible patients (30-70 years) with type 2 diabetes on 14 general practitioner lists. Measures: SF-36 response rates, distribution of dimension scores and internal consistency. Median scores in relation to sociodemography and self-reported health. Comparisons with ADDQoL scores. Results: One hundred and thirty-one patients responded (71%). Distributions of SF-36 dimension scores were mostly skewed. Internal consistency and construct validity were acceptable, with predictable sociodemographic trends. People with illness related to or unrelated to diabetes scored significantly lower on most dimensions. SF-36 dimension scores correlated best with relevant diabetes-specific ADDQoL scores amongst respondents reporting no comorbidity. Conclusions: Although valid and reliable, SF-36 scores are strongly affected by non-diabetic comorbidity in type 2 diabetes, supporting the complementary use of a diabetes-specific measure, providing information about the impact of diabetes specifically.