Studies on immunological assay of vitamin K dependent factors. II. Comparison of four immunoassay methods with functional activity of protein C in human plasma

British Journal of Haematology
S Mikami, E G Tuddenham

Abstract

We describe and compare five assay systems for Protein C (PC) in human plasma; a functional assay for PC activity, Laurell electroimmunoassay with EDTA or calcium (EDTA-Laurell or Ca-Laurell), radioimmunoassay (RIA) and immunoradiometric assay (IRMA). The lower limit of sensitivity of PC in normal reference plasma was 2 X 10(-3) units/ml by RIA and 1 X 10(-4) units/ml by IRMA, but the ratio of maximum binding to blank binding was superior in RIA. In normal plasma (n = 20), there was no significant discrepancy of PC levels between RIA, Laurell (EDTA- and Ca-) and functional assay. In normal serum, PC antigen (PC:AG) measured by Ca-Laurell showed a high value (1.37 +/- 0.24 units/ml) compared to the other assays. PC:AG of a purified sample increased its level by Ca-Laurell method during activation by thrombin. Activated PC (PCa) has decreased affinity for anti-PC rabbit IgG, similarly to decarboxy (warfarinized) PC. In warfarin-treated individuals (n = 12) who were anticoagulated orally for more than 3 weeks, functional activity was lower (0.27 +/- 0.12 units/ml) than that measured by RIA (0.64 +/- 0.12 units/ml) or EDTA-Laurell (0.62 +/- 0.06 units/ml), whereas PC:AG measured by CA-Laurell had a normal value of 0.96 +/- 0.40 uni...Continue Reading

References

Aug 28, 1982·Lancet·P M Mannucci, S Vigano
Apr 1, 1981·Proceedings of the National Academy of Sciences of the United States of America·B Dahlbäck, J Stenflo
Mar 1, 1984·The New England Journal of Medicine·U SeligsohnS I Rapaport
Dec 15, 1983·Thrombosis Research·R B Francis, M J Patch
Nov 1, 1981·The Journal of Clinical Investigation·J H GriffinC Wideman

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Citations

Feb 11, 2012·International Journal of Laboratory Hematology·P C CooperR M Maclean
Sep 18, 2012·International Journal of Laboratory Hematology·I MackieUNKNOWN British Committee for Standards in Haematology
Nov 30, 1987·Clinica Chimica Acta; International Journal of Clinical Chemistry·D K Strickland, C M Kessler
Oct 1, 1989·Baillière's Clinical Haematology·G DolanF E Preston

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