Evaluation of the Diabetes Self-Care Scale.

The purpose of this study was to evaluate the psychometric properties of the Diabetes Self-Care Scale (DSCS). A convenience sample of 175 adults with diabetes who met the inclusion criteria from a local hospital in southern Louisiana participated in this study. Data from a pilot study with 50 respondents were also used to calibrate the instrument. The analysis tested the hypothesis that the difference between any respondent's agreement with an item and the difficulty presented by that item is equal to the natural logarithm of the odds of a response. Results indicated that respondent separation reliability is acceptable (.80) and item separation reliability is high (.99). All 35 items measure a single construct of diabetes self-care. Construct validity was supported by the meaningfulness of the item endorsability order and by the consistency of that order across respondents. Seven recommendations for modification of the instrument, future research, and practice are proposed.

Evaluation of the diabetes self care scale: an illustration of the Rasch model of measurement.

This pilot study illustrates the use of a Rasch measurement model to evaluate the psychometric properties of the Diabetes Self Care Scale (DSCS). A convenience sample of 50 adults with diabetes at two local hospitals (one for profit and one public) in southern Louisiana responded to the survey questions. The instrument is comprised of 27 items and 6 rating categories. The Bigsteps Rasch measurement software was used for all analyses. Results indicated that respondent separation reliability was low (0.63), but item separation reliability was satisfactory (0.91). Internal validity was supported. Twenty-six items measure a single construct of diabetes self care. Construct validity was supported by the meaningfulness of the item difficulty order and by the consistency of that order across respondents. Rating scale analysis revealed that middle categories were not distinct steps in the progression of increasing diabetes self care. In addition to deleting an item producing inconsistent responses and combining adjacent categories (categories 1 and 2, and categories 3, 4, and 5), four recommendations for future research are provided.