The large "kit-to-kit" variation in insulin radioimmunoassay is mainly due to difference in standard concentration.
D006801:Humans; D007328:Insulin / Q000097:blood* / Q000592:standards; D011786:Quality Control; D011863:Radioimmunoassay; D011933:Reagent Kits, Diagnostic / Q000592:standards*; D012015:Reference Standards
D007328:Insulin; D011933:Reagent Kits, Diagnostic