Prolongation of the Interval Between Monitoring of Warfarin in Stable Patients

NCT00356759 | Completed Phase 2 Results DMC

• 1 other identifier: PSI-06-21
• Study Type: interventional
• Target: 250
• Locations: 1 country
• Sites: 1

Brief Summary

Patients with mechanical heart valve prosthesis or with irregular beat (atrial fibrillation) have a high risk of blood clot formation. Such clots can result in a stroke. The patients are treated with warfarin - a "blood thinner" - to prevent these complications. The treatment has to be monitored with a blood test called Prothrombin time (PT) every 1-4 weeks. The dose of warfarin has to be changed whenever the PT result is outside of the treatment range. If the result is too low there is an increased risk of blood clots. If, instead, the result is too high there is a risk of bleeding. One third of the patients have very stable PT results and hardly ever have to change the dose. The investigators hypothesis is that these patients can go less often, e.g. every 12 weeks, for the blood tests.

Conditions

Atrial Fibrillation; Heart Valve Diseases; Venous Thrombosis

Keywords

warfarin; prothrombin time; monitoring

Outcome Measures

Primary Outcomes (1)

• Primary Outcome Measure: Time in Therapeutic Range

  Percent time in therapeutic range calculated by linear interpolation.

  12 months

Secondary Outcomes (5)

• Secondary Efficacy Outcomes: Thromboembolic Events

  12 months

• Secondary Safety Outcome: Major Bleeding

  12 months

• Secondary Safety Outcome: Number of Patients With Extreme INR Results

  12 months

• Number of Extreme INR Results

  12 months

• Patients With Dose Changes

  12 months

Study Arms (2)

12-weekly INR

SHAM COMPARATOR

Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times

Drug: Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times

Standard management

NO INTERVENTION

Dosing warfarin every 4 weeks, all INRs true values

Interventions

Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times DRUG

Warfarin is dosed according to INR to maintain INR 2.0-3.0 or for mechanical mitral valves or mechanical aortic valves with atrial fibrillation INR 2.5-3.5

Also known as: warfarin, Coumadin

12-weekly INR

Eligibility Criteria

• Age: 18 Years+
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Patients on long-term warfarin (for prophylaxis of arterial embolism in patients with atrial fibrillation or mechanical heart valve replacement, or secondary prophylaxis after VTE) with a target INR of 2.0-3.0 or 2.5-3.5,
• Anticoagulant therapy managed by the clinic (HHS - General Hospital) for at least 6 months prior to enrolment, and
• Maintenance dose of warfarin unchanged for the previous 6 months or longer.

You may not qualify if:

• Age \<18 years,
• Life expectancy of less than 1 year,
• Attending physician believes the patient is not suitable for the study (e.g. psychiatric disorder, history of non-compliance),
• Geographic inaccessibility or
• Failure to obtain written consent.

Sponsors & Collaborators

• Hamilton Health Sciences Corporation: lead
• The Physicians' Services Incorporated Foundation: collaborator

Study Sites (1)

HHS - General Hospital, Thrombosis Service

Hamilton, Ontario, L8L 2X2, Canada

Location

Related Publications (1)

• Schulman S, Parpia S, Stewart C, Rudd-Scott L, Julian JA, Levine M. Warfarin dose assessment every 4 weeks versus every 12 weeks in patients with stable international normalized ratios: a randomized trial. Ann Intern Med. 2011 Nov 15;155(10):653-9, W201-3. doi: 10.7326/0003-4819-155-10-201111150-00003.

  PMID: 22084331 DERIVED

MeSH Terms

Conditions

Atrial Fibrillation; Heart Valve Diseases; Venous Thrombosis

Interventions

Warfarin

Condition Hierarchy (Ancestors)

Arrhythmias, Cardiac; Heart Diseases; Cardiovascular Diseases; Pathologic Processes; Pathological Conditions, Signs and Symptoms; Thrombosis; Embolism and Thrombosis; Vascular Diseases

Intervention Hierarchy (Ancestors)

4-Hydroxycoumarins; Coumarins; Benzopyrans; Pyrans; Heterocyclic Compounds, 1-Ring; Heterocyclic Compounds; Heterocyclic Compounds, 2-Ring; Heterocyclic Compounds, Fused-Ring

Limitations and Caveats

Not a truly INR monitoring and dosing every 12 weeks, because patients were tested and contacted every 4 weeks for sham results and to remind of important factors for INR instability. Extreme INR results in the 12-week group were reported unblinded.

Results Point of Contact

• Title: Dr. Sam Schulman
• Organization: McMaster University

schulms@mcmaster.ca

19055270271

Study Officials

• Sam Schulman, Professor

  McMaster University

  PRINCIPAL INVESTIGATOR

Publication Agreements

• PI is Sponsor Employee: Yes

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: RANDOMIZED
• Masking: TRIPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Prof.

Study Record Dates

• First Submitted: July 24, 2006
• First Posted: July 26, 2006
• Study Start: December 1, 2006
• Primary Completion: January 1, 2010
• Study Completion: February 1, 2010
• Last Updated: August 22, 2018
• Results First Posted: August 22, 2018

Record last verified: 2018-08

Data Sharing

• IPD Sharing: Will not share

Locations

CA (1)