How do you identify patients with false positive AcHR antibodies?

First of all, of course, one should look for the clinical correlation. Even a weakly positive AchR binding antibody is likely to be "real" (true positive) if accompanied by unequivocal clinical signs of MG, e.g., fatigable ptosis with positive ice pack test, or fatigable bulbar/limb weakness. Ideally, in patients presenting with weakness and showing weakly positive AchR binding antibodies, electrophysiologic studies such as RNS or single-fiber EMG should be performed to confirm the diagnosis.

If ...