Changes of Acetylcholine Receptor Antibody Concentration and Disease Severity in Myasthenia Gravis

ABSTRACT

The authors have measured the anti-AChR antibody concentration in sera of 20 myasthenia gravis and of 17 normal or other neurological diseases, to establish the radioimmunoassay(RIA) system for the AChR antibody test and to evaluate the possible relationships between changes in AChR antibody titer and clinical severity of myasthenia gravis. Significant AChR antibody titers(more than 0.04 pmol/ml) were found in 17 out of 20 myasthenia gravis (85.0%) and in 1 out of 17 norrnal or other neurological diseases (5.9%). When those 20 myasthenia gravis were classified into Ossennan's clinical stage, the AchR antibody titer rarlged from 0 to 059 pmole/ml in grade I, from 0.01 to 0.68 pmole/ml in grade IIA, from 0.15 to 1.05 pmole/ml in grade II and from 0.22 to 1.03 pmol/ml in grade III, and showed relatively good correlation with clinical severity of myasthenia gravis (Pearson correlation coef{icient 0.76). However the correlation proved to be better when the AChR antibody titers were compared with the functional activities of myasthenia gravis according to Drachman s proposal. Also the authors thought that the AChR antibody tests would be invaluable in the diagnosis of myasthenia gravis and that the extensive studies would be needed to establish the normal value of the binding AChR antibody in our laboratory.