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Simple Warfarin Dosing Algorithm Study (KT-INR)

This study has been completed.
ClinicalTrials.gov Identifier:
First Posted: November 5, 2009
Last Update Posted: July 22, 2011
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.
Information provided by:
Population Health Research Institute

Can a simple and cost-free tool help family physicians to improve dosing of the blood thinner warfarin?

Warfarin is a blood thinner with a variable effect and requires regular blood monitoring and dose adjustments. Some family practices do not have the facilities or funding to use commercial tools than can assist with stabilizing the effect of warfarin. The investigators will test whether a simple and cost-free dosing tool can help these practices to improve warfarin management.

If this simple tool improves warfarin management, it will be freely available for practices in Canada and around the world. This will help physicians who have no access to more costly and/or complicated tools improve their warfarin dosing practice in a systematic fashion, and thereby maximize the health benefit of warfarin.

Condition Intervention
Warfarin Dosing Other: Algorithm

Study Type: Interventional
Study Design: Allocation: Randomized
Intervention Model: Parallel Assignment
Masking: Single (Participant)
Primary Purpose: Treatment
Official Title: Cluster Randomized Trial to Assess the Effect of Using a Simple Warfarin Maintenance Dosing Algorithm on the Quality of INR Control Among Canadian Family Practices

Resource links provided by NLM:

Further study details as provided by Population Health Research Institute:

Primary Outcome Measures:
  • Mean time in therapeutic range for patients [ Time Frame: 1 Year ]

Secondary Outcome Measures:
  • Proportion of patients with TTR > 65% [ Time Frame: 1 Year ]
  • Correlation between algorithm adherence and TTR [ Time Frame: 1 Year ]
  • Among patients in both baseline and study sample: proportion of patients with TTR improvement [ Time Frame: 1 Year ]

Enrollment: 553
Study Start Date: October 2009
Study Completion Date: June 2011
Primary Completion Date: April 2011 (Final data collection date for primary outcome measure)
Arms Assigned Interventions
Experimental: Algorithm
Algorithm (available in paper version and web-based version) will be used for warfarin maintenance dosing.
Other: Algorithm
Warfarin Dosing algorithm (paper and electronic version)
No Intervention: Care as usual
Control group

Detailed Description:
Warfarin reduces the risk of thromboembolism, but requires regular blood monitoring to keep the international normalized ration (INR) within a narrow therapeutic range to achieve maximum benefits. A low proportion of time spent within the therapeutic INR range, (TTR) is associated with reduced warfarin efficacy and potentially harmful results. To optimize TTR, international guidelines recommend the use of systematic evidence-based dosing methods (anticoagulation clinic, computerized systems, manual algorithm and patient self-management). A survey in the Hamilton area revealed that half of family physicians manage warfarin dosing without assistance from an evidence-based method. The simple manual dosing algorithm is a simple tool that helped increase the TTR at the Hamilton General Hospital's anticoagulant clinic to an excellent 73% among patients with target INR range 2-3. We will test whether the simple dosing algorithm can help to improve warfarin dosing of family physicians who are not assisted by evidence-based methods. We will randomize family practices to either use the simple dosing algorithm or to manage warfarin dosing as usual, to test whether the simple dosing algorithm achieves a superior TTR.

Information from the National Library of Medicine

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Ages Eligible for Study:   18 Years and older   (Adult, Senior)
Sexes Eligible for Study:   All
Accepts Healthy Volunteers:   No

Inclusion Criteria:

  • Family practices that:

    1. currently do not employ an evidence-based dosing method (anticoagulant clinic, computer system, manual algorithm or patient self-testing),
    2. manage warfarin maintenance dosing in at least 10 patients with target INR 2-3, and
    3. have at least one family physician providing written informed consent.
  • Patients who:

    1. are on long-term warfarin treatment (> 6 weeks before study entry and expected to continue for at least 6 more months) with target INR 2-3, for whom warfarin is managed by a participating family physician,
    2. patient provides written informed consent.

Exclusion Criteria:

  • Family practices that:

    1. are planning to start employing an evidence-based method for warfarin dosing within the next year,
    2. are not expected to enroll at least 10 patients on long-term warfarin treatment with target INR 2-3.
  • Patients:

    1. with < 3 months warfarin management prior to the baseline observation,
    2. patients on warfarin with a target INR other than 2-3, and
    3. patients for whom warfarin is managed by a physician who is not participating in the trial.
  Contacts and Locations
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 ClinicalTrials.gov identifier (NCT number): NCT01008215

Canada, Ontario
Caroline Medical Group
Burlington, Ontario, Canada, L7R 4C7
Sponsors and Collaborators
Population Health Research Institute
Principal Investigator: Stuart Connolly McMaster University
  More Information

Responsible Party: Dr. Stuart Connolly, McMaster University
ClinicalTrials.gov Identifier: NCT01008215     History of Changes
Other Study ID Numbers: 09-282
First Submitted: October 28, 2009
First Posted: November 5, 2009
Last Update Posted: July 22, 2011
Last Verified: July 2011

Keywords provided by Population Health Research Institute:
INR Control
Warfarin dosing
Family physicians
Cluster randomization

Additional relevant MeSH terms: