[Which therapy comparisons are fair?]

Two approaches to treatment comparison are discussed: According to the principles of evidence-based medicine (EBM), methods of comparison are graded on a study-type scale, with randomised controlled trials and meta-analyses of randomised trials ranking at the highest levels. In contrast, cognition-based medicine (CBM) is based on the physician's recognition of causality of a treatment in the individual patient. A careful examination of potential sources of misinterpretation reveals that none of these approaches enforces fairness of comparisons: Randomised controlled trials often cannot be generalised, meta-analyses are based on retrospectively-selected studies and exposed to the ecological fallacy, and CBM approaches are not sufficiently controlled. Thus, fairness does not result from the choice of a perfect method or from the tailoring of the evaluation method to the therapy under examination. Rather, a complementary approach of different evaluation methods with all treatments to be compared should be used, with open discussion of strengths and weaknesses of the approaches applied in each particular case.