At long last, the current test for JRD offered by Doggenes and subsequently by Laboklin has been publically criticised.
http://www.plosone.org/article/info%253Adoi%252F10.1371%252Fjournal.pone.0016684

We had been banging our heads against a  brick wall as flatcoats had very dubious results since the 'test' was introduced.      Eventually someone has taken our criticisms on board.    But it does make us wonder about the validity of other tests.

Jo