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 (APTT) assay, Dahlback 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 approaches 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 ions. 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 VR506Q than the APTT- APC-Resistance test.
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Authors | L E Hoagland, D A Triplett, F Peng, L Barna |
Journal | Thrombosis research
(Thromb Res)
Vol. 83
Issue 5
Pg. 363-73
(Sep 01 1996)
ISSN: 0049-3848 [Print] United States |
PMID | 8873345
(Publication Type: Journal Article)
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Chemical References |
- Anticoagulants
- Elapid Venoms
- Phospholipids
- Protein C
- factor V Leiden
- textilotoxin
- Factor V
- Prothrombin
- Heparin
- Calcium
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Topics |
- Anticoagulants
(pharmacology)
- Blood Coagulation Tests
- Calcium
(blood)
- Disease Susceptibility
- Elapid Venoms
(pharmacology)
- Enzyme Activation
- Factor V
(genetics, metabolism)
- Factor V Deficiency
(blood, epidemiology, genetics)
- Heparin
(pharmacology)
- Humans
- Incidence
- Partial Thromboplastin Time
- Phospholipids
(blood)
- Point Mutation
- Polymerase Chain Reaction
- Protein C
(metabolism)
- Prothrombin
(drug effects)
- Reference Values
- Sensitivity and Specificity
- Thromboembolism
(blood, epidemiology, etiology, prevention & control)
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