Measurement of health status in diabetic patients. Diabetes impact measurement scales

Abstract

Objective: To develop an instrument to measure health status in adult insulin-dependent (type I) and non-insulin-dependent (type II) diabetic patients.

Research design and methods: Correlative study to examine psychometric properties of the questionnaire. Test-retest reliability, item-scale correlations, principal-components analysis, correlations with global clinical ratings, and correlations with clinical data extracted from medical records were examined at the diabetes clinics at the University of California, Davis, Medical Center. Patients were volunteer clinic patients able to complete the questionnaire. One hundred thirty patients completed a first administration of the questionnaire, and 52 completed a second administration.

Results: Test-retest reliability was satisfactory. Item-scale correlations showed that 40 of 44 questionnaire items were highly correlated with subscale and total scale scores. Principal-components analysis identified one major factor measured by the questionnaire. Cronbach's alpha, a measure of the scales' internal consistency, was of satisfactory magnitude. Global ratings of clinical status by patients and clinicians were highly correlated with scale scores. Correlations of scale scores with clinical data were generally of low magnitude but, where significant, were consistently in the direction hypothesized if the scale truly measures health status or disease impact.

Conclusions: The Diabetes Impact Management Scales (DIMS) is an easily administered questionnaire with internal consistency and test-retest reliability. Preliminary correlative analyses support the validity of the instrument as a measure of health status in adult type I and type II diabetic patients. Further work will be necessary to firmly establish the validity of the DIMS and its usefulness in clinical outcomes research.