Quantitation of free, total, and antibody bound insulin in insulin treated diabetics

Abstract

The authors describe a simplified method for measuring free, total, and antibody bound insulin in insulin treated patients in whom antibodies to insulin are present. The free, active insulin is extracted from the serum with a polyethylene glycol solution. Total insulin is extracted from the serum with a polyethylene glycol solution after dissociation of the antibody antigen complex with dilute HCl. Aliquots of the extracts are used in the radioimmunoassay system. The figure for antibody bound insulin is the difference between the total and free insulin values and reflects the concentration of insulin antibodies present. A commercially available ('Phadebas') radioimmunoassay for immunoreactive insulin was used to quantitate the insulin present in the two extracts. Recovery of added insulin averaged 85% for the free insulin and 87% for the total insulin.