INS and type 1 diabetes mellitus: It is still controversial if proinsulin rather than insulin is the primary autoantibody.<h4>Methods</h4>The aim of the present study was to compare the half-maximal concentration (IC50) between insulin and proinsulin to displace the binding of insulin to insulin autoantibodies (IAA) in the Antibody Detection by Agglutination PCR (ADAP) assay.<h4>Results</h4>IC50 as a measure of potency to displace insulin binding to IAA was determined in 36 newly diagnosed type 1 diabetes children.