Any drug that suppresses the immune system can, in theory, make the antibody and SF/EMG tests look negative. Why? Because that's what they are supposed to do!

It can still be positive but from what I've heard from MG experts, if your MG is "new" or more mild, it can be negative but an antibody level does not necessarily predict how the clinical presentation of MG will be. There is no way to predict if it will affect your tests or not.

Annie