Relationship between patient-practice oriented knowledge and metabolic control in intensively treated Type 1 diabetic patient: Result of the validation of the knowledge and Practices Diabetes Questionnaire

AIMS: To validate a newly developed questionnaire for the measurement of patients' knowledge and practices, with particular attention to its ability in predicting HbA1c levels. RESEARCH DESIGN AND METHODS: The Knowledge and Practices Diabetes Questionnaire (KPDQ) is a questionnaire composed of two scales, investigating patient knowledge and practices. Twenty-two questions, 12 dealing with patients' knowledge and 10 relative to patients' practices, were initially identified. Factor analysis and reliability analysis were used to validate the questionnaire. The ability of the two scales in predicting metabolic control was then evaluated. The questionnaire was administered to a population of Type 1 diabetic subjects intensively treated and regularly attending the diabetes outpatient clinic of Pescara General Hospital. The mean of all HbA1c measurements performed after patients were taken in charge by the clinic was used as an indicator of metabolic control. RESULTS: Out of 133 Type 1 patients identified, 77 (58 %) filled in the questionnaire. Respondents had a mean age (+/- SD) of 37 +/- 13 years and a mean diabetes duration of 13 +/- 9 years. The application of factor and reliability analyses led to the definition of two final scales composed of 10 (Knowledge Score, KS) and 5 items (Practice Score, PS), respectively. Item-scale correlation was > or = 0.40 for all the items investigated. Cronbach's alpha coefficient exceeded the value of 0.70 for both scales. The mean number of HbA1c determinations during a median period of observation of 4 years was of 11 +/- 5. The mean HbA1c value for the whole population was of 7.0% +/- 1.4, while the proportion of patients with values < or = 7.0% was of 57%. After adjusting for clinical and patient-related characteristics, the KS was the only independent predictor of metabolic control. Patients in the lowest quartile of the KS showed a more than 20-fold increased risk of having mean HbA1c values > or = 7.0% as opposed to those in the highest quartile (odds ratio, OR=23.3;p=0.009). No association emerged between metabolic control and PS. CONCLUSIONS: The KPDQ presents excellent psychometric properties. The KS also shows a very impressive association with the mean HbA1c values over a period of 4 years. These findings are particularly remarkable in that many studies have failed in documenting such a relationship. The KS can thus be considered as a quick and efficient screening tool to be used in an ambulatory setting to monitor the level of practice-oriented knowledge of patients with Type 1 diabetes as well as to identify those subjects who need individualized educational interventions.