There's no real consensus, the idea of Devic's as a separate disease is still pretty new. It's hard to do any research on as it's so rare. I am one of the handful of sufferers in my country (dad always told me I was special ). Multiple doctors still refer to me as having MS - and I do too sometimes when trying to explain it to laypeople, it's just easier. The IgG test is positive in about 70% of Devic's cases so it's by no means a miracle diagnostic tool - mine was negative for example. MRI still remains the test with the highest specificity for diagnosing any demyelinating condition.