[Can individual experience be considered for efficacy assessment?]

The question is discussed whether the efficacy assessment of a therapy can be modified by the observation of a different outcome in individual cases. N-of-1 studies may help to decide between different options in special individual circumstances. Case series have their role in medicine, especially for generating hypothesis. But the observation of isolated cases can be no substitute for efficacy assessment through clinical trials, which are based on a systematic compilation and statistical analysis of many individual cases.