The Construct Validity of an Instrument for Measuring Type 2 Diabetes Self-Care Knowledge in Nigeria

Purpose: To develop an instrument (DSCKQ-30) for measuring type 2 diabetic patients’ knowledge of self-care practices. Methods: A 30-item questionnaire (DSCKQ-30) consisting of close ended questions was developed for this study. DSCKQ-30 was self administered to a cross-section of randomly selected 400 ambulatory adult diabetic patients (≥ 18 years), who were attending endocrinology clinics at the hospitals included in this study. The sex distribution for female and male was 56.7 and 43.3% respectively. Factor analysis and item analysis were performed to test the construct validity and reliability of the instrument. Item performance was measured by item discrimination (item-to-total correlation) and percent correctness (%C). Results: The response rate was 78.5%. Factor analysis identified three scales of knowledge of self-care management. Chronbach’s alpha of the 30 questionnaire items was found to be 0.89. The item-to-total correlation coefficients and ranges for component 1 - 3 were 0.36 (0.25 - 0.48), 0.28 (0.23 - 0.35), and 0.34 (0.23 - 0.41), respectively, with overall average of 0.33 (0.23 - 0.48). Items percent correctness (%C) ranged from 16.7 to 86.7 % with an overall average of 55.6 %. Item factor loadings averaged 0.62 for the total items; averages of the three scales ranged from 0.59 to 0.68. Conclusion: The DSCKQ-30 provided a quantitative measure of patient s knowledge of self-care practices.