Study of Genetic Factors Other Than CYP2C9 and VKORC1 That Influence Warfarin Dose Requirements in a South-east Asian Population

The safety and scientific validity of this study is the responsibility of the study sponsor and investigators. Listing a study does not mean it has been evaluated by the U.S. Federal Government. Read our disclaimer for details. Identifier: NCT01050920
Recruitment Status : Unknown
Verified January 2014 by National University Hospital, Singapore.
Recruitment status was:  Recruiting
First Posted : January 18, 2010
Last Update Posted : January 22, 2014
Information provided by:
National University Hospital, Singapore

Brief Summary:
Warfarin is a commonly used anti-coagulant, but has a narrow therapeutic index and wide inter-individual and inter-ethnic variation in dose requirements. Several genetic and non-genetic factors have been identified that could influence warfarin dose requirements. However, current known predictive factors could only explain about 50-60% of warfarin dose variability. Inter-ethnic differences in genetic influences on warfarin dose requirements also exist. We hypothesize that genetic factors other than CYP2C9 and VKORC1 may influence warfarin dosing and serve to further optimize warfarin dosing.

Condition or disease Intervention/treatment
Cancer Biological: Blood collection

Study Type : Observational
Observational Model: Cohort
Time Perspective: Cross-Sectional
Study Start Date : September 2013
Estimated Primary Completion Date : December 2014
Estimated Study Completion Date : December 2014

Resource links provided by the National Library of Medicine

MedlinePlus related topics: Blood Thinners
U.S. FDA Resources

Group/Cohort Intervention/treatment
Blood Collection Biological: Blood collection

Primary Outcome Measures :
  1. To identify genetic variants other than CYP2C9 and VKORC1 that may influence warfarin dose requirements in a multi-ethnic population in Singapore.

Information from the National Library of Medicine

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Ages Eligible for Study:   21 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No
Sampling Method:   Probability Sample
Study Population

Germline DNA will be genotyped for variants in genes in the anti-coagulation pathway, including CYP4F2, GGCX and EPHX1. The germline DNA was previously collected from a warfarin study (C/00/510, NUH, C/00/535, TTSH, PI-Dr Goh Boon Cher). Samples were anonymized, and data analysis will be done without patient identifiers. Germline DNA previously collected from 279 patients who were on maintenance warfarin dose will be genotyped.

The clinical data that has been collected and will be used for the study include: gender, race, age, body weight, maintenance warfarin dose, serum albumin, two consecutive stable INR values, and indications for warfarin use.


Inclusion Criteria:

  • patients receiving maintenance warfarin therapy with a stable therapeutic international normalized ratio (INR) between 2 and 3 for at least 3 months,
  • patients recruited from the anticoagulation clinics at the National University Hospital and Tan Tock Seng Hospital in Singapore between June 2002 and June 2004 for a previous genotyping study (C/00/510, NUH; C/00/535, TTSH, PI-Dr Goh Boon Cher).

Exclusion Criteria:

  • patients below 21 years old, or
  • patients with liver disease, malabsorption or chronic diarrheal diseases, or
  • patients taking drugs that may potentially interact with warfarin.

Dietary advice to avoid foods that may interfere with warfarin pharmacokinetics will be given to patients during warfarin therapy.

Information from the National Library of Medicine

To learn more about this study, you or your doctor may contact the study research staff using the contact information provided by the sponsor.

Please refer to this study by its identifier (NCT number): NCT01050920

Contact: Soo Chin Lee, MBBS, MRCP 65 6772 4629

National University Hospital Recruiting
Singapore, Singapore, 119074
Contact: Soo Chin Lee, MBBS, MRCP    65 6772 4629   
Sponsors and Collaborators
National University Hospital, Singapore