Development and psychometric assessment of a manufacturer independent knowledge questionnaire on real time continuous glucose monitoring for insulin-treated people with diabetes

Abstract

Abstract Background To benefit from real time continuous glucose monitoring (rtCGM), users need practical skills and in-depth knowledge to analyse the glucose data appropriately and adapt insulin therapy accordingly. To assess the user’s knowledge about rtCGM, a psychometric knowledge test was developed and evaluated. Method Experts on the use of rtCGM systems defined central knowledge contents in a Delphi process and developed a knowledge test comprising 40 multiple-choice items. For test-statistical review, people with insulin-treated diabetes and members of diabetes teams answered the knowledge test. Results The 122 members of diabetes team (age 46 (11) years; mean (SD)) and the 111 people with insulin-treated diabetes (age 42 (14) years, diabetes duration 20 (14) years, insulin treatment with pumps 64 %, previous usage of CGM 38 %, HbA1c 8.0 % [95 %-KI 7.7–8.3]; 64 mmol/mol [60–67]) had different levels of experiences using rtCGM-systems. The internal consistency (Cronbach’s alpha) of the knowledge test was 0.92 for the whole sample, for people with diabetes 0.94, and for members of the diabetes teams 0.84. Item difficulty ranged between 0.12 and 0.88 in people with diabetes and between 0.27 and 0.97 among members of diabetes teams. On average, people with diabetes answered 24.1 (9.9) items correctly, members of diabetes team 29.2 (5.2) (p < 0.001); people with diabetes and previous rtCGM-experience had a higher knowledge than people without previous experience (29.2 (6.2) vs. 21.0 (10.4) (p = 0.001)). The quality of glucose control (measured by HbA1c) of the people with diabetes was significantly associated with the sum-score of the questionnaire (rho = -0.48, p < 0.001). Conclusion The knowledge test „rtCGM-Profi-Check“ provides a high internal consistency, high selectivity and content validity. It is suitable for objective, reliable and valid assessment of the indispensable knowledge of people with diabetes to use different rtCGM systems successfully. The questionnaire is manufacturer independent and can be used to evaluate the needs and success of rtCGM-education among persons with diabetes.