Document Detail

Evaluation of the phospholipid-rich dilute Russell's viper venom assay to monitor oral anticoagulation in patients with lupus anticoagulant.
MedLine Citation:
PMID:  15166923     Owner:  NLM     Status:  MEDLINE    
The International Normalized Ratio (INR) is generally recommended to monitor anticoagulant therapy in patients treated with warfarin. However, there has been concern about the validity of the INR to monitor warfarin therapy in patients with lupus anticoagulant, particularly when there is prolongation of the baseline INR. An alternative approach is to use a chromogenic factor X assay that is not sensitive to lupus anticoagulant. However, this assay is expensive, not widely available, and does not have an established therapeutic range. We hypothesized that the phospholipid-rich dilute Russell viper venom time (prdRVVT), a simple, rapid and inexpensive assay, might be suitable to monitor warfarin therapy in this situation since Russell's viper venom directly activates coagulation factor X while the phospholipid in the reagent reduces or negates any effect of lupus anticoagulant on the assay. We measured the INR, chromogenic factor X, and prdRVVT in 50 patients stabilized on warfarin for at least 6 weeks, 12 of whom had lupus anticoagulant, and 37 patients not taking warfarin, 17 of whom had lupus anticoagulant. Factor X was negatively correlated with INR in anticoagulated patients both in the absence (r = -0.45, P = 0.01) and presence (r = -0.43, P = 0.17) of lupus anticoagulant. The prdRVVT was also strongly correlated with INR in anticoagulated patients without lupus anticoagulant (r = 0.60, P < 0.0001) but there was no correlation in the presence of lupus anticoagulant (r = -0.13, P = 0.68). Our results suggest that the prdRVVT is not suitable for monitoring warfarin therapy in patients with lupus anticoagulant.
Jim Thom; Leesa Ivey; Grace Gilmore; John W Eikelboom
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Publication Detail:
Type:  Evaluation Studies; Journal Article    
Journal Detail:
Title:  Blood coagulation & fibrinolysis : an international journal in haemostasis and thrombosis     Volume:  15     ISSN:  0957-5235     ISO Abbreviation:  Blood Coagul. Fibrinolysis     Publication Date:  2004 Jun 
Date Detail:
Created Date:  2004-05-28     Completed Date:  2005-02-16     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9102551     Medline TA:  Blood Coagul Fibrinolysis     Country:  England    
Other Details:
Languages:  eng     Pagination:  353-7     Citation Subset:  IM    
Coagulation and Thrombosis Unit, Department of Haematology, Royal Perth Hospital, Perth, Western Australia, Australia.
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MeSH Terms
Anticoagulants / blood*,  therapeutic use
Blood Coagulation Tests
Case-Control Studies
Drug Monitoring / methods*
Indicators and Reagents
Lupus Coagulation Inhibitor / blood*
Prothrombin Time / methods,  standards*
Warfarin / blood,  therapeutic use
Reg. No./Substance:
0/Anticoagulants; 0/Indicators and Reagents; 0/Lupus Coagulation Inhibitor; 0/Phospholipids; 81-81-2/Warfarin

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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