Undercarboxylated osteocalcin and development of a method to determine vitamin K status

Lori J. Sokoll, Maureen E. O'Brien, Maria E. Camilo, James A. Sadowski

Research output: Contribution to journalArticlepeer-review

40 Scopus citations


We developed a RIA involving a polyclonal antibody against bovine osteocalcin, which has a carboxy-terminal epitope. Although the antibody recognizes both native and descarboxy osteocalcin, the two forms of osteocalcin were differentiated by adsorption to barium sulfate, taking advantage of the calcium-binding properties of the vitamin K-dependent gla domain. To test the clinical application of undercarboxylated osteocalcin, we examined the effect of minidose warfarin on this measure in nine healthy subjects, ages 60 to 80 years. The percentage of undercarboxylated osteocalcin increased by 170% ± 36% (mean ± SE) after 7 days of treatment with warfarin, 1 mg/day. The effectiveness of undercarboxylated osteocalcin as a sensitive measure of vitamin K nutritional status was further established when concentrations dropped to 17% ± 14% below baseline with 2 days of repletion with vitamin K1, 5 mg/day, during which prothrombin times did not leave the normal range.

Original languageEnglish (US)
Pages (from-to)1121-1128
Number of pages8
JournalClinical chemistry
Issue number8
StatePublished - 1995


  • anticoagulants
  • nutritional status
  • radioimmunoassay
  • warfarin

ASJC Scopus subject areas

  • Clinical Biochemistry
  • Biochemistry, medical


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