Long‐term Correlation of Clinical Course and Acetylcholine Receptor Antibody in Patients With Myasthenia Gravis

Abstract

Antibodies (Ab) to acetylcholine receptors ( AchR) are instrumental in bringing about the neuromuscular defect in myasthenia gravis (MG) . The demonstration of Ab by immunoprecipitation assay proved to be highly specific, of great diagnostic value, and in good correlation to clinical improvement in MG patients on plasma exchange therapy.l, Only little information is available in the long term correlation between intraindividual AB titers and clinical course.2 This study presents a group of 99 MG patients (41 male, 58 female; mean age 45, five years) followed up for 36 months, using a new, simple and reproducible MG-Score (see TABLE 1 ) and serial measurements of Ab titers by a modified immunoprecipitation assay.3To calculate the correlation of Ab titer and clinical course, relative changes of MG-Score in individual patients and the differences in normalized Ab titers of the identical interval were plotted against each other. Each interval of usually one to two months was analyzed separately. (Bivariate plotting program BMDP6D by H.C.S.F. U.C.L.A. 1977, adapted to a Siemens 4004/151 computer.) The correlation is calculated in different groups of MG patients, referring to age, sex and duration as well as to MG patients with mild (MG-Score <1.0) and marked (MG-Score >1 .O j disease.We found a high correlation between Ab titer and clinical course in serial measurements of patients with moderate and marked MG. In contrast there was no correlation in patients with mild disease. No influence of age and sex of MG-patients or duration of the disease upon this correlation could be demonstrated. Long-term observations of individual patients generally showed a close correlation between MG-Score and serially determined Ab titer. In about 10% of the severely affected MG patients however rising Ab titers could be demonstrated without immediate increase in MG-Score. In those patients deterioration could be detected within three weeks to three months. The MG-Score used in this study is a simple and reliable tool for the clinical follow-up of MG patient as well as for long term investigations. From our * Correspondence address for U. A. Besinger includes Moehlstrasse 28 8000 Munich

Neuromuscular function and plasma drug levels in pyridostigmine treatment of myasthenia gravis.

“…Other patients either did not show an impairment of neuromuscular transmission or their clinical state did not allow them to carry out the measurement (three cases). The decrement that attained maximal values of -10 to -57% in the total group changed by at least 10% (maximum change 30%/-) in 10 cases.…”

History of outcome measures for myasthenia gravis

“…The first ordinal rating scale for MG (“MG Score”) was developed in the 1980s 52–54. The MG‐Score was a standardized outcome instrument that measured endurance of outstretched limbs and of neck lift, time to development of ptosis and dysconjugate gaze, eye closure strength, degree of grip strength decrement measured using a dynamometer, vital capacity, and frequency and severity of symptoms of chewing and swallowing fatigue and weakness 52–54. A slightly modified MG numerical scale was used as one of the primary outcome measures in a trial that demonstrated the efficacy of cyclosporine in MG 55, 56.…”

“…[52][53][54] The MG-Score was a standardized outcome instrument that measured endurance of outstretched limbs and of neck lift, time to development of ptosis and dysconjugate gaze, eye closure strength, degree of grip strength decrement measured using a dynamometer, vital capacity, and frequency and severity of symptoms of chewing and swallowing fatigue and weakness. [52][53][54] A slightly modified MG numerical scale was used as one of the primary outcome measures in a trial that demonstrated the efficacy of cyclosporine in MG. 55,56 This scale was modified once more in the late 1990s, notably by replacing subjective assessments of speech and swallowing taken from the history with more objective tests of counting aloud to 50 and swallowing 4 ounces of water (Supporting Table 3). 57 The cyclosporine trials 55,56 and QMG interrater reliability testing [57][58][59] suggested that a three-point change in QMG score should be considered significant.…”

Standards of Measurements in Myasthenia Gravis

“…The current quantitative MG scoring system (QMG Score) is an expansion and modification of the tool developed by Besinger et al 12,13 (Table 2). The original scoring system consisted of 8 items, each graded 0 to 3, with 3 being the most severe.…”