APC-resistance as measured by a Textarin time assay: Comparison to the APTT-based method

L. E. Hoagland, Douglas A. Triplett, F. Peng, L. Barna

Research output: Contribution to journalArticle

16 Scopus citations

Abstract

Protein C is a major regulatory protein critical to physiologic anticoagulation. When activated, it selectively degrades the activated forms of factors V and VIII, thereby, down-regulating blood coagulation. Using an activated partial thromboplastin time (ATPP) assay, Dahlbeck et al. recently reported that some individuals with thrombophilia show a poor in vitro anticoagulant response to activated protein C (APC-Resistance). Subsequent studies identified a point mutation in the gene for factor V as the underlying cause of APC-Resistance. The incidence of APC-Resistance in patients with recurrent thromboembolic events approached 50%. The APC-Resistance phenotype is also present in approximately 5% of normal Caucasian subjects. In an attempt to develop a more sensitive and specific test system, we evaluated an assay based on Textarin®(Pentapharm, Basel, Switzerland). Textarin®, a protein fraction of Pseudonaja textilis venom (Australian Eastern Brown Snake) activates prothrombin in the presence of phospholipid (PL), factor V and calcium ion. Based on Textarin's requirement for factor V, we developed a Textarin time assay to test for APC-Resistance. We evaluated this test system in normal subjects and the following patient populations: stable orally anticoagulated, previously diagnosed factor V Leiden, and therapeutically heparinized samples. We found the Textarin assay to be a sensitive and specific test system to identify APC-Resistance. The phenotypic Textarin APC-Resistance test correlated more closely with the genotypic abnormality of factor V(506Q) than the APTT-APC-Resistance test.

Original languageEnglish (US)
Pages (from-to)363-373
Number of pages11
JournalThrombosis research
Volume83
Issue number5
DOIs
StatePublished - Sep 1 1996

Keywords

  • Activated protein C resistance
  • Factor V mutation
  • Textarin®

ASJC Scopus subject areas

  • Hematology

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