BACKGROUND: The clinical values of neostigmine test, clinical electrophysiologic study and acetylcholine receptor antibody detection in diagnosing myasthenia gravis (MG) found newly are unclear in China. OBJECTIVE: To investigate the reference value of common clinical diagnosis parameters in correctly diagnosing untreated MG found newly. DESIGN: Retrospective case analysis. SETTING: Department of Neurology, Beijing Hospital, Ministry of Health. PARTICIPANTS: Totally 156 outpatients with MG admitted to Department of Neurology, Beijing Hospital, Ministry of Health between January 1999 and December 2002. The involved patients, 72 males and 84 females, were aged 2–79 years. They were classified according to Osserman’s criteria: ⅡA 72,ⅡB 76, Ⅲ 3 and Ⅳ 5. They were all subjected to being inquired of disease history, neostigmine test, and acetylcholine receptor antibody detection, met the diagnosis criteria of Neuroimmunology Committee of China, and confirmed by clinical electrophysiologic detections; Informed consents were obtained from all the involved subjects. METHODS: ①After admission, every patient was intramuscularly injected with 1.5 mg neostigmine; If the patient was a child, the injection dose was decreased according to his/her age. If his/her score of any observation index after injection was improved ≥ 50% as compared with before injection , his positive index was set as positive. Positive neostigmine test was set if there was one positive index. ②Repetitive nerve stimulation and single fiber electromyography were performed with Dantec Keypoint electromyogram (EMG) apparatus. ③Acetylcholine receptor antibody was detected by ELISA method. MAIN OUTCOME MEASURES: Clinical absolute and relative scores of MG, acetylcholine receptor antibody level, and repetitive nerve stimulation and single fiber electromyography examination results. RESULTS: The positive rates of neostigmine test, repetitive nerve stimulation and single fiber electromyography examination for MG were 86.5%, 82.6%, and 69.2%, respectively, and the positive rate of acetylcholine receptor antibody was 78.8%. CONCLUSION: Standardized neostigmine test has the highest sensitivity to diagnose MG. BACKGROUND: The clinical values ​​of neostigmine test, clinical electrophysiologic study and acetylcholine receptor antibody detection in diagnosed myasthenia gravis (MG) found newly are unclear in China. OBJECTIVE: To investigate the reference value of common clinical diagnosis parameters in correctly diagnosed untreated MG found newly SETTING: Department of Neurology, Beijing Hospital, Ministry of Health. PARTICIPANTS: Totally 156 outpatients with MG admitted to Department of Neurology, Beijing Hospital, Ministry of Health between January 1999 and December 2002. The involved patients, 72 males and 84 females, were aged 2-79 years. They were all under intoocused of disease history, neostigmine test, and acetylcholine receptor antibody detection, met the diagnosis criteria of Neuroimmunology Committee of China, and confirmed by clinical electrophys METHODS: ①After admission, every patient was intramuscularly injected with 1.5 mg neostigmine; If the patient was a child, the injection dose was decreased according to his / her age. If his / her score of any observation index after injection was improved ≥ 50% as compared with before injection, his positive index was set as positive. Positive Repetitive nerve stimulation and single fiber electromyography were performed with Dantec ③ ACtylcholine receptor antibody was detected by ELISA method. MAIN OUTCOME MEASURES: Clinical absolute and relative scores of MG, acetylcholine receptor antibody level, and repetitive nerve stimulation and single fiber electromyography examination results. RESULTS: The positive rates of neostigmine test, repetitive nerve stimulation and single fiber electromyography exam ination for MG were 86.5%, 82.6%, and 69.2%, respectively, and the positive rate of acetylcholine receptor antibody was 78.8%. CONCLUSION: Standardized neostigmine test has the highest sensitivity to diagnose MG.