Failure of ultracentrifugation as a means of separating plasma free insulin from immunoglobulin fraction prior to radioimmunoassay

Luis J. Escobar, Neil H. White, Julio V. Santiago, Ronald L. Gingerich

Research output: Contribution to journalArticlepeer-review

Abstract

It has been reported that ultracentrifugation of plasma will allow direct measurement of free insulin in the serum of diabetic subjects with insulin antibodies. To validate this method, we determined recovery of immunoreactive insulin and immunoglobulin G from the plasma of normal individuals after ultracentrifugation. The upper and middle fractions of plasma after ultracentrifugation were evaluated at several combinations of time and temperature (4°C, 25°C, or 37°C for 3, 4 or 5 hours). None of these conditions effectively removed all immunoglobulin G without causing concomitant loss of insulin. We conclude that ultracentrifugation of plasma prior to radioimmunoassay cannot be used to reliably determine free insulin concentration in the plasma from subjects with circulating insulin antibodies.

Original languageEnglish
Pages (from-to)11-15
Number of pages5
JournalClinica Chimica Acta
Volume152
Issue number1-2
DOIs
StatePublished - Oct 31 1985

Keywords

  • Free insulin
  • Insulin antibodies
  • Ultracentrifugation

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