Maybe this will help. I found it on NetWellness and it is a a quote (answer) by Robert Neel, Assoc. Prof of Neurology at University of Cincinnati:

"Generalized and ocular myasthenia are clinical terms and I do not define them by antibody status. Antibody titers support a diagnosis of myasthenia, but do not make it. There are different types of antibodies that we check. Binding antibodies are most commonly checked and are found in generalized and ocular myasthenia. They are absent in roughly 50% of ocular myasthenics and 10-20% of generalized myasthenics. Blocking antibodies can also be checked. Modulating antibodies are thought to reduce acetylcholine receptors on muscle cells. They are detected in 90% of myasthenics, even when the binding antibodies are negative. But caution must always be used in making a clinical diagnosis based on a test, as the modulating antibody can be falsely positive in people who have recently taken muscle relaxants. I advise you to talk to your physician and ask him/her about what other options are available for treatment. Some of the treatment side effects are equally as bad as the disease itself. I will try to use Mestinon alone, if I can, to control the disease. Discuss his/her reservations about treatment. "