Correspondence (letter to the editor): An Unbiased Approach Is Necessary

Linder et al claim to mostly have ruled out selection biases by means of an “sophisticated control group design.” However, in order to do so one would have to approach the study subject in an unbiased fashion, otherwise even methods such as the described “propensity score matching” entail the risk that the inappropriate or incomplete patient selection criteria, which affect the model, determine the results. Against this background, readers might ask themselves why relevant comorbidities such as coronary heart diseases and arterial hypertension were not considered, or why with regard to myocardial infarction, only ICD-I21 was included, but not other relevant diagnoses. The question also needs to be asked why patients should be included in such an analysis who were registered in the T2DM for only one or a few quarters. Which effects should one expect if patients were enrolled to the dMP only for a short time? It is completely incorrect to state that the ELSID study, which is being conducted by our working group, has a “inadequate” control group design and does “not fulfill the requirements of a scientifically based study.” This is a strong statement regarding a project that in its evaluation—in contrast to Linder et al—considers overall morbidity in matching rather more comprehensively and ensures a sufficiently lengthy registration period before drawing conclusions about effectiveness. Although further development of the T2DM is needed in some aspects (for example, in order to focus on high risk patients) and improvements to its implementation are necessary, there are now many study results that show improved healthcare provision (1) and a higher degree of activation of the patients (2). This seems to benefit in particular older and multimorbid diabetes patients—exactly those patients who constitute the majority of those affected. Not to mention the important impulse that the DMPs provide for practice teams (especially doctors and other medical professionals) to further professionalize their dealings with chronically ill patients and to further develop internal practice structures (3).