title: Antibodies to glutamic acid decarboxylase in Syrian and Jordanian type I diabetes patients and their siblings.
abstract: BACKGROUND
  Attempts to identify the earliest events in the autoimmune process in type I diabetes mellitus suggests the glutamic acid decarboxylase (GAD) is one of the first and most important autoantigens. We conducted this study to determine the prevalence of antibodies to glutamic acid decarboxylase (anti-GAD) in both Syrian and Jordanian children with Type I diabetes and their siblings.
  
  
  METHODS
  sera were obtained from 85 Syrian patients with type I diabetes (mean age 13.6 + 5.9 years), from 45 of their siblings (mean age 11 + 6.1 years), from 78 randomly selected Syrian control subjects (mean age 9.9 + 43 years), and from 95 Jordanian patients with type I diabetes (mean age 13.9 + 65 years), from 78 of their siblings (mean age 12.3 + 7.1 years), and from 100 randomly selected Jordanian control subjects (mean age 7.8 + 4.5 years). Sera were analyzed from anti-GAD using the enzyme linked immunosorbent assay (ELISA) technique.
  
  
  RESULTS
  Prevalence of anti-GAD was 34.1% (29/85) in Syrian type I diabetes patients, 20% (9/45) in their siblings, 1.3% (1/78) in Syrian control subjects, 49.5% (47/95) in Jordanian type I diabetes patients, 23% (18/78) in their siblings, and 2% (2/100) in Jordanian control subjects. Differences between the Syrian and Jordanian type I diabetes groups and their siblings and controls were statistically significant. In patients with less than two years of diabetes duration, the frequency was 88.8% (16/18) for both groups. There was no correlation between sex and anti-GAD levels in their Syrian and Jordanian type I diabetes patients and their siblings. The positivity of anti-GAD tended to be more frequent at the age range of 5 to 8 years in siblings. Anti-GAD titers >90 ng/ml were found in 58.8% of type I diabetes patients and in 38% of siblings who were anti-GAD positive.
  
  
  CONCLUSIONS
  Syria and Jordan have prevalence rates of anti-GAD among type I diabetes patients and their siblings that are among the highest reported in the world. Therefore, anti-GAD may be valuable as an early predictive marker for type I diabetes.
authors.affiliation: Faculty of Medicine, University of Jordan, Amman, Jordan.
authors.forename: Mohammed S
authors.initials: MS
authors.lastname: El-Khateeb
authors.forename: Shadwan
authors.initials: S
authors.lastname: Mesri
authors.forename: Muhieddin
authors.initials: M
authors.lastname: Juma
authors.forename: Mohamed
authors.initials: M
authors.lastname: El-Zaheri
authors.forename: Kamel
authors.initials: K
authors.lastname: Ajlouni