DIAGNOSIS MG:

Diagnostic tests:

Anti-AChR antibodies in serum.
Anti-MuSK antibodies. Held in all study patients with anti-acetylcholine receptor negative.
Thyroid function. Performed on all patients, since it is a common comorbidity.
Neurophysiological study. It helps to establish the diagnosis in patients with suspected seronegative MG.

  4.a. Repetitive stimulation at low frequencies (2-5 Hz): greater than 75% sensitivity if performed at proximal zones, specificity 89% -98%. Pathological test is considered when there is a decrease of more than 10% of the amplitude or the fourth or fifth area evoked motor potential compared to the first.

4.b. Single fiber electromyography: sensitivity 92%, specificity low as I can be altered pathology of nerve and muscle.

Brain MRI: seronegative patients with ocular symptoms consistent with MG may have structural brain pathology.
TC (MRI) Chest: in all patients with suspected MG, regardless of the distribution (eye / generalized) or serology (HIV positive / seronegative).
Tensilon test or Edrophonium.
Test ice.
If all tests are negative and have ruled out other diagnostic possibilities, with poor response to immunomodulatory treatment, congenital MG suspect.

Monitoring of antibody titers:

     There is a good correlation between the levels of anti-AChR antibodies and clinical. However it may be advisable to have the level of antibodies in patients with MG with anti-AChR antibodies as it can provide guidance on the degree of immunosuppression.

      There is a good positive correlation between the titers of anti-MuSK antibody and severity of the disease and it has been shown that the immunosuppressive treatment produces a decrease in antibody titer.