I am student of medicine. We have conducted a study to assess the association between a gene and migraine disorder. A reviewer from a journal has said that "The design (people with disease vs those without) is known to be associated with a very significant positive bias for the test. Case-control studies like this are useful but can be misleading in ascribing a power to the diagnostic". We have selected migraine patients and healthy subjects to compare. Please help me about the comment of the reviewer.