title: Clinical and serological study of myasthenia gravis using both radioimmunoprecipitation and cell-based assays in a South Asian population.
abstract: BACKGROUND
  Identification of autoantibodies has defined distinct clinico-immuno-pathological subtypes of myasthenia gravis (MG) such as AChR-antibody-positive-MG and MuSK-antibody-positive-MG. The use of more sensitive assays such as the cell-based assay (CBA) is expected to reduce the proportion of seronegative-MG. We studied the seroprevalence of AChR and MuSK antibodies using both radioimmunoprecipitation (RIA) and CBA amongst MG patients in Sri Lanka and related their antibody status to their clinical subtypes and severity.
  
  
  METHODS
  113 patients with MG attending Neurology units in the district of Colombo were studied. Clinical data were obtained using an interviewer-administered questionnaire and medical records. The severity of MG was assessed according to MGFA clinical grading. RIA and CBA were used to detect serum AChR and MuSK antibodies. Patients with other neurological diseases were recruited as controls.
  
  
  RESULTS
  We detected either AChRAb (85%) or MuSKAb (6.2%) in 91.2% of MG patients. Complementing the RIA with the CBA improved the diagnostic power of detecting AChRAbs by 21% and MuSKAbs by 77%. The clinical characteristics and the occurrence of thymic pathology were similar to other populations except for a male preponderance (1.5:1). The AChRAb titer appeared to parallel the clinical severity. Seven of 11 (63.6%) patients with AChRAb-negative generalized MG had MuSK-MG.
  
  
  CONCLUSIONS
  Clinical characteristics of MG in Sri Lanka are similar to other populations. Complementing the RIA with CBA increases the diagnostic power of detecting pathogenic autoantibodies.
authors.affiliation: Department of Clinical Medicine, University of Colombo, Sri Lanka. Electronic address: thashichang@gmail.com.
authors.forename: Thashi
authors.initials: T
authors.lastname: Chang
authors.affiliation: Department of Clinical Neurology, University of Oxford, United Kingdom.
authors.forename: Maria Isabel
authors.initials: MI
authors.lastname: Leite
authors.affiliation: Neurology Unit, North Colombo Teaching Hospital, Sri Lanka.
authors.forename: Sunethra
authors.initials: S
authors.lastname: Senanayake
authors.affiliation: Institute of Neurology, National Hospital, Colombo, Sri Lanka.
authors.forename: Padma S
authors.initials: PS
authors.lastname: Gunaratne
authors.affiliation: Institute of Neurology, National Hospital, Colombo, Sri Lanka.
authors.forename: Ranjanie
authors.initials: R
authors.lastname: Gamage
authors.affiliation: Neurology Unit, Colombo South Teaching Hospital, Sri Lanka.
authors.forename: M T M
authors.initials: MT
authors.lastname: Riffsy
authors.affiliation: Department of Clinical Neurology, University of Oxford, United Kingdom.
authors.forename: Leslie W
authors.initials: LW
authors.lastname: Jacobson
authors.affiliation: Department of Clinical Medicine, University of Colombo, Sri Lanka.
authors.forename: Madura
authors.initials: M
authors.lastname: Adhikari
authors.affiliation: Department of Clinical Medicine, University of Colombo, Sri Lanka.
authors.forename: Sanja
authors.initials: S
authors.lastname: Perera
authors.affiliation: Department of Clinical Neurology, University of Oxford, United Kingdom.
authors.forename: Angela
authors.initials: A
authors.lastname: Vincent
mesh_terms: D000328:Adult; D001323:Autoantibodies / Q000097:blood*; D005260:Female; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D057809:HEK293 Cells; D006801:Humans; D008297:Male; D008875:Middle Aged; D009157:Myasthenia Gravis / Q000097:blood / Q000175:diagnosis / Q000276:immunology; D015531:Radioimmunoprecipitation Assay; D020794:Receptor Protein-Tyrosine Kinases / Q000235:genetics / Q000276:immunology*; D011950:Receptors, Cholinergic / Q000235:genetics / Q000276:immunology*; D016036:Seroepidemiologic Studies; D013188:Sri Lanka; D014162:Transfection / Q000379:methods
chemical_list: D001323:Autoantibodies; D011950:Receptors, Cholinergic; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D020794:Receptor Protein-Tyrosine Kinases
keywords: AChR; Antibodies; MuSK; Myasthenia gravis; Sri Lanka