Minimal clinically important difference for pain on the VAS scale and the relation to quality of life in women with endometriosis.

•The minimal important difference can be helpful in interpreting data from clinical trials.•The minimal important difference for improvement on the VAS scale was found to be −39mm and −49%.•The cut off for success in trials is suggested to be an either >40mm or a >50% decrease on VAS scale.•If the level for success is set too low it might be difficult to exclude the placebo effect.