Immunoglobulin G insulin autoantibodies in BABYDIAB offspring appear postnatally: Sensitive early detection using a protein A/G-based radiobinding assay

Insulin autoantibodies (IAA) are early sensitive markers of prediabetes in the young. The aim of this study was to assess whether, using IgG-specific measurement with a protein A/G assay, IAA are already present at birth, and whether this assay is suitable for early autoantibody screening. Cord bloo d and follow-up samples from offspring of parents with type 1 diabetes incl uded in the BABYDIAB study were analyzed. Although insulin antibodies in co rd blood from children of mothers with type I diabetes were readily detecte d and correlated well with levels in the maternal circulation, no insulin b inding was detected in 247 cord blood samples from children of father proba nds. IgG EAA were detected at 2 yr in all 21 children who had multiple isle t autoantibodies or who later developed type 1 diabetes, but were confirmed in only 6 of 58 with IAA by the conventional IAA assay in the absence of o ther islet autoantibadies. False positive IAAs in the conventional assay we re often attributable to hemolysis. Hemolysis did not affect protein A/G IA A measurement, and results in whole capillary blood samples were comparable to those in corresponding serum samples (r(2) = 0.99). These data show tha t IgG IAA appear early and after birth, and that the protein A/G IAA assay is sufficiently sensitive for early screening. The specificity of this assa y requires further evaluation.