Background: AChR antibodies (Abs) in Myasthnia Gravis (MG) are detected in approximately 50% of ocular and 85% of generalized MG by the current gold standard radioimmunoprecipitation assay (RIPA). Recently, fixed and lived Cell-Based assays (L-CBA) are developed. We clinically validated our in-house L-CBA in detecting AChR Ab in clinically suspected MG patients. Methods: Between January 2020 and April 2022, we assayed 10167 sera for AChR Ab by RIPA. We also assayed 4349 of AChR Ab seronegative sera of the above suspected MG samples for anti-MuSK Ab by RIPA. Then 1228 sera of double seronegative and/or borderline AChR Ab was assessed by L-CBA for AChR Ab. For clinical validation, we obtained clinical information on 36 seropositive cases for AChR Ab by L-CBA. Results: We found additional eighty-four cases seropositive for AChR Ab by L-CBA. The clinical information was obtained for 36 cases and based on their final diagnosis, twenty had generalized MG, thirteen had ocular MG, 2 not yet diagnosed and 1 case was of not-MG. Conclusions: The L- CBA has demonstrated improved sensitivity and higher diagnostics performance than RIPA. The L-CBA allowed improved clinical diagnosis and increased seropositivity (by 7%) in clinically suspected MG patients who were earlier seronegative/borderline for AChR Ab by RIPA.