The effect of immediate polyethylene glycol precipitation on free insulin measurements in diabetic patients with insulin antibodies

Abstract Diabetic patients receiving insulin therapy generally develop anti-insulin antibodies that must be eliminated, usually by extraction with polyethylene glycol (PEG), before determining the concentration of free (active) insulin in plasma. We describe a new method for removing such antibodies, with the use of Protein A coupled to Sepharose microspheres. The results correlate well with those by the PEG method, although values are systematically higher or lower for given samples, according to the initial titer of the antibody measured in terms of binding capacity. Further studies are required to clarify this observation.

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Quantitation of Free, Total, and Antibody-bound Insulin in Insulin-Treated Diabetics

Clinical Chemistry ◽

10.1093/clinchem/21.7.873 ◽

1975 ◽

Vol 21 (7) ◽

pp. 873-879 ◽

Cited By ~ 41

Author(s):

William D Gennaro ◽

John D Van Norman

Keyword(s):

Polyethylene Glycol ◽

Insulin Antibodies ◽

Immunoreactive Insulin ◽

Simplified Method ◽

Free Insulin ◽

Antigen Complex ◽

The Difference ◽

Glycol Solution

Abstract We 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.

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Influence of Polyethylene Glycol (PEG) Extraction on the C-Peptide Determination in Sera from Insulin-Dependent Diabetic Patients with Circulating Insulin Antibodies*)

Experimental and Clinical Endocrinology & Diabetes ◽

10.1055/s-0029-1210943 ◽

2009 ◽

Vol 95 (01) ◽

pp. 119-122 ◽

Cited By ~ 4

Author(s):

W. Besch ◽

H. Keilacker ◽

K.-D. Kohnert ◽

M. Ziegler

Keyword(s):

Polyethylene Glycol ◽

Insulin Antibodies ◽

Diabetic Patients ◽

C Peptide ◽

Insulin Dependent ◽

Insulin Dependent Diabetic

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Diagnosis of self-induced hyperinsulinism in an insulin-dependent diabetic patient by radioimmunoassay of free C-peptide.

Clinical Chemistry ◽

10.1093/clinchem/27.1.184 ◽

1981 ◽

Vol 27 (1) ◽

pp. 184-186 ◽

Cited By ~ 4

Author(s):

M T Meistas ◽

M S Kumar ◽

O P Schumacher

Keyword(s):

Polyethylene Glycol ◽

Diabetic Patient ◽

Insulin Antibodies ◽

Self Administration ◽

C Peptide ◽

Free Insulin ◽

Insulin Dependent ◽

Insulin Dependent Diabetic ◽

Antigen Antibody ◽

Plasma Free Insulin

Abstract On the basis of results of simultaneous determinations of plasma free insulin and free c-peptide, episodes of hypoglycemia in an insulin-dependent diabetic were attributed to surreptitious self-administration of insulin. Immunoreactive c-peptide values were falsely increased and diagnostically misleading when measured in unextracted plasma. After preliminary removal of antigen/antibody complexes from the plasma by extraction with polyethylene glycol, the c-peptide values, referred to as "free c-peptide," were suppressed. We suggest that insulin antibodies formed complexes with proinsulin-like material in the plasma of this patient, which accounted for most of the c-peptide immunoreactivity in her unextracted plasma. These complexes must be removed if c-peptide measurements are to be accurate.

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