Strengths and limitations
decline of measured HbA1c levels, diabetes
REGRESSION, DIABETES
One of the key strengths of the DEBATE trial is its long time of follow-up with a total period of 24 months. The follow-up period of previous diabetes management studies was often less than two years [The results of this study should be considered in the context of several important limitations. One is the subjective data collection of individualized treatment goals. GPs have been asked once at baseline (via questionnaire), whether they had defined a target value together with the patient. No research was done on how the GPs involved the patient in the decision-making process. No standardized procedure was given, which makes comparison between groups difficult. HbA1c target values should be closely coordinated with the patient and adjusted as needed [Our analysis has shown a decline of measured HbA1c levels in both groups (shared vs. non-shared) over two years. However, the clinical relevance is low. It remains unclear to what extent the decline might be ‘regression towards the mean’.Furthermore, the potential impact of selection bias remains unclear. It can be assumed that mainly motivated and interested GPs and patients participated in the study. We cannot exclude that mainly GPs, who were already practicing SDM were included in the study. This might have diminished the effects of the DEBATE intervention as well as the group differences presented in this article. It also might have affected the external validity of the study. As no information had been collected on GPs and patients not participating in the study, the extent of a selection bias cannot be estimated.The results of our study show, that regardless of how the HbA1c target value was set (shared or not), HbA1c levels among both groups improved. This may be due to natural reductions in patients, who were selected for their maximum HbA1c. Another reason could be the occurrence of the Hawthorne effect [Furthermore, we did not examine routine GP patient care. The GPs were free in their decision to change the medication. The effect of treatment escalation on the achievement of shared vs. non-shared HbA1c goals was not investigated. However, the main analysis of the DEBATE trial shows no effect of changes in medication on HbA1c levels [