Thromb Haemost 1997; 77(03): 481-485
DOI: 10.1055/s-0038-1655993
Coagulation
Schattauer GmbH Stuttgart

Reliability of a Modified Tissue Factor-Dependent Factor V Assay for Activated Protein C Resistant Factor Va Using a Calcium-Containing Thromboplastin

Dzung The Le
The Department of Pathology, University of California, San Diego, California, USA
,
Kathleen J Donnelly
The Department of Pathology, University of California, San Diego, California, USA
,
Ning Wu
The Department of Pathology, University of California, San Diego, California, USA
,
Barbara K Sevilla
The Department of Pathology, University of California, San Diego, California, USA
,
Samuel I Rapaport
1   The Department of Medicine and Pathology, University of California, San Diego, California, USA
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Publikationsverlauf

Received 12. April 1996

Accepted after resubmission 18. November 1996

Publikationsdatum:
11. Juli 2018 (online)

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Summary

The original tissue factor-dependent factor V assay for activated protein C resistant factor Va (Blood 1995; 85: 1704-1711) has been modified to use a calcium containing thromboplastin and to express results as an observed to expected ratio (Obs./Exp.). The latter permits establishing a normal range independent of variations due to differences in reagents. Comparing Obs/Exp ratios with DNA analysis in 72 persons revealed that an Obs/Exp ratio of 0.6 distinguished without overlap normals from heterozygotes for FV R506Q. Three homozygotes had a ratio of <0.1. Application of this Obs/Exp cut-off ratio of 0.6 to a total of 226 plasma samples tested to date discriminated without overlap between normals and heterozygotes. We conclude that this assay – readily adaptable to any dedicated coagulation laboratory and capable of yielding reliable results in all clinical circumstances in which testing is indicated – can distinguish between normals and heterozygotes for the FV R506Q mutation without the need for confirmatory DNA analysis.