Radioimmunoassay May Overestimate Insulin in Non-Insulin-Dependent Diabetics

Clin Endocrinol (Oxf). 1990 Jun;32(6):689-93. doi: 10.1111/j.1365-2265.1990.tb00915.x.


We have compared insulin concentrations measured by radioimmunoassay (RIA) in plasma from 50 fasting non-insulin-dependent diabetics (NIDDM) with those measured by a new monoclonal antibody-based two-site immunoradiometric assay (IRMA) of insulin (which has no significant cross-reaction with proinsulin-like molecules). We find that the RIA measures the sum of the insulin and proinsulin like molecules and that the IRMA insulin concentrations are 38% of those measured by the RIA in those diabetic subjects. We conclude that the importance of insulin deficiency in NIDDM may have been obscured by this error.

Publication types

  • Comparative Study
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Blood Glucose / analysis
  • Cross Reactions
  • Diabetes Mellitus / blood
  • Diabetes Mellitus, Type 2 / blood*
  • Female
  • Humans
  • Immunoradiometric Assay
  • Insulin / blood*
  • Insulin / immunology
  • Male
  • Middle Aged
  • Obesity
  • Proinsulin / blood
  • Radioimmunoassay


  • Blood Glucose
  • Insulin
  • Proinsulin