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Dispersion of mean consecutive differences in single‐fiber electromyography increases diagnostic sensitivity for myasthenia gravis
Author(s) -
Kojima Yuta,
Shibuya Kazumoto,
Uzawa Akiyuki,
Kano Hiroki,
Nakamura Keigo,
Yasuda Manato,
Suzuki Yoichi,
Tsuneyama Atsuko,
Suichi Tomoki,
Ozawa Yukiko,
Misawa Sonoko,
Noto Yuichi,
Mizuno Toshiki,
Kuwabara Satoshi
Publication year - 2021
Publication title -
muscle and nerve
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.025
H-Index - 145
eISSN - 1097-4598
pISSN - 0148-639X
DOI - 10.1002/mus.27236
Subject(s) - myasthenia gravis , receiver operating characteristic , medicine , youden's j statistic , coefficient of variation , nuclear medicine , area under the curve , standard deviation , gastroenterology , chemistry , mathematics , chromatography , statistics
In this study we aimed to investigate the dispersion of mean consecutive difference (MCD) of concentric needle jitter studies of patients with myasthenia gravis (MG) and its effect on diagnostic sensitivity for MG. Methods One hundred fifty‐three patients, including 76 patients with MG and 77 controls with possible MG who later received another diagnosis, underwent stimulated concentric needle jitter studies of the frontalis muscle. MCD mean, standard deviation (SD), and coefficient of variation (CV) were calculated. Diagnostic sensitivity and specificity were determined using receiver operating characteristic (ROC) analyses. Results MG patients showed a significantly greater MCD mean (MG: control, 26.3 μs; 13.5 μs [median]; P < .0001), MCD SD (MG: control, 12.8 μs; 5.1 μs [median]; P < .0001), and MCD CV (MG: control, 46.1; 37.5 [median]; P < .001) than those without MG. An ROC curve of SD showed a large area under the curve (0.88), and a cut‐off value of 7.2 μs, which was calculated by maximum Youden index, exhibited high diagnostic sensitivity (86%) for MG. Combined MCD mean, outliers, and SD criteria showed higher sensitivity (88%) than conventional criteria alone (82%), at the expense of lower specificity. Five MG patients with normal MCD mean and abnormal MCD SD had only ocular symptoms. Discussion The dispersion of MCD as measured by MCD SD greater than 7.2 μs is significantly increased in patients with MG and may be a useful measure of abnormal jitter in the diagnosis of MG, especially for identifying patients with mild disease.