Assay of plasma 25-hydroxy vitamin D

J. F. Morris, M. Peacock

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37 Scopus citations


A radio-competitive protein-binding assay for 25-hydroxy vitamin D3 (25-OHD3) is described using diluted plasma from patients with vitamin D deficient osteomalacia as the binding protein. The 25-OHD3 is extracted from plasma with ethanol and assayed directly without further purification. An incubation of two hours is used to give suitable binding. The lower detection limit of the assay is approximately 23 pg, the intra-assay coefficient of variation is 5.4% and the inter-assay variation 15%. The range of plasma 25-OHD3 in 35 normal subjects is 5.04-72.5 μg/l with a mean of 26.9 μg/l- Levels of plasma 25-OHD3 are undetectable in patients with vitamin D deficient osteomalacia and greater than 1100 μg/l in patients taking large doses of vitamin D2.

Original languageEnglish (US)
Pages (from-to)383-391
Number of pages9
JournalClinica Chimica Acta
Issue number3
StatePublished - Nov 1 1976

ASJC Scopus subject areas

  • Biochemistry
  • Clinical Biochemistry
  • Biochemistry, medical

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