[Roaming through methodology. IX. The interpretation of subgroup analyses].

The results of subgroup analyses can be very informative, in particular for clinicians interested in evidence pertaining most directly to a particular patient. However, subgroup analyses may also be potentially misleading. The strength of evidence for subgroup effects depends on the question whether hypotheses have been defined prior to analysis, whether potential problems regarding multiple comparisons have been considered and whether there is biological plausibility of the effects. Using these guidelines the reader of a trial report should be able to decide if presented subgroup effects are of clinical importance or if the overall result is a better estimate of treatment effect.