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Radioimmunoassay for quantitative measurement of factor VIII‐heavy chain
Author(s) -
Nordfang O.,
Ezban M.,
Nilsson P.,
Knudsen J. B.
Publication year - 1988
Publication title -
british journal of haematology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.907
H-Index - 186
eISSN - 1365-2141
pISSN - 0007-1048
DOI - 10.1111/j.1365-2141.1988.tb04207.x
Subject(s) - radioimmunoassay , medicine
Summary An immunoassay has been developed for the measurement of factor VIII heavy chain (FVIII‐HC). IgG from a human inhibitor plasma with specificity for FVIII‐HC and FVIII‐light chain (FVIII‐LC) was coated to microplates with loose wells. After washing, the plates were incubated with sample and after another wash 125 I‐FVIII‐HC was added so that the amount of bound tracer was dependent on the amount of FVIII‐HC in sample. When EDTA was included in the assay buffer the assay response was increased 3‐fold for normal human plasma. This indicated that the antibody was reactive with a determinant hidden in the FVIII‐HC/FVIII‐LC complex as EDTA splits the complex. The sensitivity of the assay was 0.004 units/ml (1 unit/ml in normal human plasma pool). Together with a previously published assay for FVIII‐LC it has now become possible to measure the relative amounts of FVIII‐HC and FVIII‐LC in haemophilia A plasma and to study the separate expression of FVIII‐HC and FVIII‐LC by recombinant DNA technology. Patients with severe haemophilia A had FVIII‐HC levels below 0.01 units/ml. However, inhibitor patients in high dose FVIII‐treatment showed up to 50 times higher levels of FVIII‐HC than FVIII‐LC and FVIII:C, indicating the presence of FVIII/anti‐FVIII‐LC immune complexes. Thus, dependent on assay specificity plasma samples can show very variable content of FVIII:antigen.