Ignite Creation Date:
2025-12-24 @ 2:53 PM
Ignite Modification Date:
2025-12-26 @ 7:02 AM
Study NCT ID:
NCT00356759
Status:
COMPLETED
Last Update Posted:
2018-08-22
First Post:
2006-07-24
Is NOT Gene Therapy:
True
Has Adverse Events:
True
Brief Title:
Prolongation of the Interval Between Monitoring of Warfarin in Stable Patients
Sponsor:
Organization:
Raw JSON
{'hasResults': True, 'derivedSection': {'miscInfoModule': {'versionHolder': '2025-12-24'}, 'conditionBrowseModule': {'meshes': [{'id': 'D001281', 'term': 'Atrial Fibrillation'}, {'id': 'D006349', 'term': 'Heart Valve Diseases'}, {'id': 'D020246', 'term': 'Venous Thrombosis'}], 'ancestors': [{'id': 'D001145', 'term': 'Arrhythmias, Cardiac'}, {'id': 'D006331', 'term': 'Heart Diseases'}, {'id': 'D002318', 'term': 'Cardiovascular Diseases'}, {'id': 'D010335', 'term': 'Pathologic Processes'}, {'id': 'D013568', 'term': 'Pathological Conditions, Signs and Symptoms'}, {'id': 'D013927', 'term': 'Thrombosis'}, {'id': 'D016769', 'term': 'Embolism and Thrombosis'}, {'id': 'D014652', 'term': 'Vascular Diseases'}]}, 'interventionBrowseModule': {'meshes': [{'id': 'D014859', 'term': 'Warfarin'}], 'ancestors': [{'id': 'D015110', 'term': '4-Hydroxycoumarins'}, {'id': 'D003374', 'term': 'Coumarins'}, {'id': 'D001578', 'term': 'Benzopyrans'}, {'id': 'D011714', 'term': 'Pyrans'}, {'id': 'D006573', 'term': 'Heterocyclic Compounds, 1-Ring'}, {'id': 'D006571', 'term': 'Heterocyclic Compounds'}, {'id': 'D006574', 'term': 'Heterocyclic Compounds, 2-Ring'}, {'id': 'D000072471', 'term': 'Heterocyclic Compounds, Fused-Ring'}]}}, 'resultsSection': {'moreInfoModule': {'pointOfContact': {'email': 'schulms@mcmaster.ca', 'phone': '19055270271', 'title': 'Dr. Sam Schulman', 'phoneExt': '44810', 'organization': 'McMaster University'}, 'certainAgreement': {'piSponsorEmployee': True}, 'limitationsAndCaveats': {'description': '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.'}}, 'adverseEventsModule': {'timeFrame': '12 months', 'description': 'Fatal events are reported as serious adverse events. Non-fatal major bleeding or thromboembolism are reported as serious adverse events. Minor bleeding events are reported as non-serious (other) adverse events.', 'eventGroups': [{'id': 'EG000', 'title': '12-weekly INR', 'description': 'Patients had INR every 4 weeks but only every thisrd INR was true; the other two were sham INRs dampened to be within or close to therapeutic range. Thus, true dose assessment was in practice performed every 12 weeks', 'otherNumAtRisk': 124, 'deathsNumAtRisk': 124, 'otherNumAffected': 7, 'seriousNumAtRisk': 124, 'deathsNumAffected': 2, 'seriousNumAffected': 4}, {'id': 'EG001', 'title': '4-weekly INR', 'description': 'Patients had INR every 4 weeks and all results were true. Thus, true dose assessments were performed every 4 weeks.', 'otherNumAtRisk': 126, 'deathsNumAtRisk': 126, 'otherNumAffected': 4, 'seriousNumAtRisk': 126, 'deathsNumAffected': 5, 'seriousNumAffected': 7}], 'otherEvents': [{'term': 'Epistaxis', 'notes': 'Bleeding from the nose that did not fulfill criteria for major bleeding', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 4, 'numAffected': 4}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Respiratory, thoracic and mediastinal disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Hematuria', 'notes': 'Urinary tract bleeding that did not meet criteria for major bleeding', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 2, 'numAffected': 2}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Renal and urinary disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Rectal bleeding', 'notes': 'Bleeding from rectum bleeding that did not meet criteria for major bleeding', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 1, 'numAffected': 1}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Gastrointestinal disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Subconjunctival bleeding', 'notes': 'Subconjunctival eye bleeding that did not meet criteria for major bleeding', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 0, 'numAffected': 0}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Eye disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}], 'seriousEvents': [{'term': 'Cardiac death', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 1, 'numAffected': 1}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 3, 'numAffected': 3}], 'organSystem': 'Cardiac disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Septic shock', 'notes': 'Pancreatitis with fatal septic shock', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 0, 'numAffected': 0}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Infections and infestations', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Respiratory failure', 'notes': 'Fatal respiratory failure', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 1, 'numAffected': 1}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Respiratory, thoracic and mediastinal disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Gastrointestinal bleeding', 'notes': 'Melena', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 2, 'numAffected': 2}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Gastrointestinal disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}, {'term': 'Renal infarct', 'notes': 'Arterial embolism', 'stats': [{'groupId': 'EG000', 'numAtRisk': 124, 'numEvents': 0, 'numAffected': 0}, {'groupId': 'EG001', 'numAtRisk': 126, 'numEvents': 1, 'numAffected': 1}], 'organSystem': 'Renal and urinary disorders', 'assessmentType': 'SYSTEMATIC_ASSESSMENT'}], 'frequencyThreshold': '0'}, 'outcomeMeasuresModule': {'outcomeMeasures': [{'type': 'PRIMARY', 'title': 'Primary Outcome Measure: Time in Therapeutic Range', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '74.1', 'spread': '18.8', 'groupId': 'OG000'}, {'value': '71.6', 'spread': '20.0', 'groupId': 'OG001'}]}]}], 'paramType': 'MEAN', 'timeFrame': '12 months', 'description': 'Percent time in therapeutic range calculated by linear interpolation.', 'unitOfMeasure': 'percentage of time', 'dispersionType': 'Standard Deviation', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat population'}, {'type': 'SECONDARY', 'title': 'Secondary Efficacy Outcomes: Thromboembolic Events', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '1', 'groupId': 'OG000'}, {'value': '0', 'groupId': 'OG001'}]}]}], 'paramType': 'NUMBER', 'timeFrame': '12 months', 'description': 'Number of patients with any objectively verified, independently adjudicated thromboembolic event during the 12-month study period', 'unitOfMeasure': 'participants', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat'}, {'type': 'SECONDARY', 'title': 'Secondary Safety Outcome: Major Bleeding', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '1', 'groupId': 'OG000'}, {'value': '2', 'groupId': 'OG001'}]}]}], 'paramType': 'NUMBER', 'timeFrame': '12 months', 'description': 'Number of patients with any objectively verified, independently adjudicated major bleeding event during the 12-month study period. Major bleeding was defined according to the International Society on Thrombosis and Haemostasis (ISTH) criteria', 'unitOfMeasure': 'participants', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat'}, {'type': 'SECONDARY', 'title': 'Secondary Safety Outcome: Number of Patients With Extreme INR Results', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '27', 'groupId': 'OG000'}, {'value': '19', 'groupId': 'OG001'}]}]}], 'paramType': 'NUMBER', 'timeFrame': '12 months', 'description': 'Secondary safety outcome is number of patients with at least one INR below 1.5 or above 4.4', 'unitOfMeasure': 'participants', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat'}, {'type': 'SECONDARY', 'title': 'Number of Extreme INR Results', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '27', 'groupId': 'OG000'}, {'value': '17', 'groupId': 'OG001'}]}]}], 'paramType': 'NUMBER', 'timeFrame': '12 months', 'description': 'Number of INRs outside the range 1.5-4.4', 'unitOfMeasure': 'Number of tests', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat'}, {'type': 'SECONDARY', 'title': 'Patients With Dose Changes', 'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'OG000'}, {'value': '124', 'groupId': 'OG001'}]}], 'groups': [{'id': 'OG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'OG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'classes': [{'categories': [{'measurements': [{'value': '70', 'groupId': 'OG000'}, {'value': '46', 'groupId': 'OG001'}]}]}], 'paramType': 'NUMBER', 'timeFrame': '12 months', 'description': 'Number of patients with at least one change of maintenance dose during the 12-month study period', 'unitOfMeasure': 'participants', 'reportingStatus': 'POSTED', 'populationDescription': 'Intention to treat'}]}, 'participantFlowModule': {'groups': [{'id': 'FG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'FG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}], 'periods': [{'title': 'Overall Study', 'milestones': [{'type': 'STARTED', 'achievements': [{'groupId': 'FG000', 'numSubjects': '126'}, {'groupId': 'FG001', 'numSubjects': '124'}]}, {'type': 'COMPLETED', 'achievements': [{'groupId': 'FG000', 'numSubjects': '112'}, {'groupId': 'FG001', 'numSubjects': '114'}]}, {'type': 'NOT COMPLETED', 'achievements': [{'groupId': 'FG000', 'numSubjects': '14'}, {'groupId': 'FG001', 'numSubjects': '10'}]}], 'dropWithdraws': [{'type': 'Death', 'reasons': [{'groupId': 'FG000', 'numSubjects': '5'}, {'groupId': 'FG001', 'numSubjects': '2'}]}, {'type': 'Withdrawal by Subject', 'reasons': [{'groupId': 'FG000', 'numSubjects': '2'}, {'groupId': 'FG001', 'numSubjects': '2'}]}, {'type': 'Adverse Event', 'reasons': [{'groupId': 'FG000', 'numSubjects': '1'}, {'groupId': 'FG001', 'numSubjects': '3'}]}, {'type': 'Lost to Follow-up', 'reasons': [{'groupId': 'FG000', 'numSubjects': '1'}, {'groupId': 'FG001', 'numSubjects': '1'}]}, {'type': 'Intercurrent disease or persistent extre', 'reasons': [{'groupId': 'FG000', 'numSubjects': '5'}, {'groupId': 'FG001', 'numSubjects': '2'}]}]}]}, 'baselineCharacteristicsModule': {'denoms': [{'units': 'Participants', 'counts': [{'value': '126', 'groupId': 'BG000'}, {'value': '124', 'groupId': 'BG001'}, {'value': '250', 'groupId': 'BG002'}]}], 'groups': [{'id': 'BG000', 'title': 'Dose Assessment 4-weekly', 'description': 'INRs and dose assessments every 4 weeks true values, no sham INRs'}, {'id': 'BG001', 'title': 'Dose Assessment 12-weekly', 'description': 'INRs and dose assessment 4-weekly, but 2 of 3 INRs are sham results, so dose assessment on true result is only 12-weekly'}, {'id': 'BG002', 'title': 'Total', 'description': 'Total of all reporting groups'}], 'measures': [{'title': 'Age, Continuous', 'classes': [{'title': 'Age', 'categories': [{'measurements': [{'value': '72', 'groupId': 'BG000', 'lowerLimit': '29', 'upperLimit': '93'}, {'value': '70', 'groupId': 'BG001', 'lowerLimit': '23', 'upperLimit': '92'}, {'value': '71', 'groupId': 'BG002', 'lowerLimit': '23', 'upperLimit': '93'}]}]}], 'paramType': 'MEDIAN', 'unitOfMeasure': 'years', 'dispersionType': 'FULL_RANGE'}, {'title': 'Sex: Female, Male', 'classes': [{'categories': [{'title': 'Female', 'measurements': [{'value': '39', 'groupId': 'BG000'}, {'value': '37', 'groupId': 'BG001'}, {'value': '76', 'groupId': 'BG002'}]}, {'title': 'Male', 'measurements': [{'value': '87', 'groupId': 'BG000'}, {'value': '87', 'groupId': 'BG001'}, {'value': '174', 'groupId': 'BG002'}]}]}], 'paramType': 'COUNT_OF_PARTICIPANTS', 'unitOfMeasure': 'Participants'}, {'title': 'Therapeutic INR range', 'classes': [{'title': 'INR range 2.0-3.0', 'categories': [{'measurements': [{'value': '111', 'groupId': 'BG000'}, {'value': '109', 'groupId': 'BG001'}, {'value': '220', 'groupId': 'BG002'}]}]}, {'title': 'INR range 2.5-3.5', 'categories': [{'measurements': [{'value': '15', 'groupId': 'BG000'}, {'value': '15', 'groupId': 'BG001'}, {'value': '30', 'groupId': 'BG002'}]}]}], 'paramType': 'NUMBER', 'description': 'International normalized ratio (INR) is a standardized expression of the prothrombin time. Normal is 0.9-1.2. Therapeutic range is 2.0-3-0 for most patients, 2.5-3.5 for those with mechanical mitral valve or with mechanical aortic valve plus atrial fibrillation', 'unitOfMeasure': 'participants'}], 'populationDescription': 'All patients randomized'}}, 'protocolSection': {'designModule': {'phases': ['PHASE2'], 'studyType': 'INTERVENTIONAL', 'designInfo': {'allocation': 'RANDOMIZED', 'maskingInfo': {'masking': 'TRIPLE', 'whoMasked': ['PARTICIPANT', 'CARE_PROVIDER', 'INVESTIGATOR']}, 'primaryPurpose': 'TREATMENT', 'interventionModel': 'PARALLEL'}, 'enrollmentInfo': {'type': 'ACTUAL', 'count': 250}}, 'statusModule': {'overallStatus': 'COMPLETED', 'startDateStruct': {'date': '2006-12'}, 'expandedAccessInfo': {'hasExpandedAccess': False}, 'statusVerifiedDate': '2018-08', 'completionDateStruct': {'date': '2010-02', 'type': 'ACTUAL'}, 'lastUpdateSubmitDate': '2018-08-21', 'studyFirstSubmitDate': '2006-07-24', 'resultsFirstSubmitDate': '2014-03-18', 'studyFirstSubmitQcDate': '2006-07-25', 'lastUpdatePostDateStruct': {'date': '2018-08-22', 'type': 'ACTUAL'}, 'resultsFirstSubmitQcDate': '2018-08-21', 'studyFirstPostDateStruct': {'date': '2006-07-26', 'type': 'ESTIMATED'}, 'resultsFirstPostDateStruct': {'date': '2018-08-22', 'type': 'ACTUAL'}, 'primaryCompletionDateStruct': {'date': '2010-01', 'type': 'ACTUAL'}}, 'outcomesModule': {'primaryOutcomes': [{'measure': 'Primary Outcome Measure: Time in Therapeutic Range', 'timeFrame': '12 months', 'description': 'Percent time in therapeutic range calculated by linear interpolation.'}], 'secondaryOutcomes': [{'measure': 'Secondary Efficacy Outcomes: Thromboembolic Events', 'timeFrame': '12 months', 'description': 'Number of patients with any objectively verified, independently adjudicated thromboembolic event during the 12-month study period'}, {'measure': 'Secondary Safety Outcome: Major Bleeding', 'timeFrame': '12 months', 'description': 'Number of patients with any objectively verified, independently adjudicated major bleeding event during the 12-month study period. Major bleeding was defined according to the International Society on Thrombosis and Haemostasis (ISTH) criteria'}, {'measure': 'Secondary Safety Outcome: Number of Patients With Extreme INR Results', 'timeFrame': '12 months', 'description': 'Secondary safety outcome is number of patients with at least one INR below 1.5 or above 4.4'}, {'measure': 'Number of Extreme INR Results', 'timeFrame': '12 months', 'description': 'Number of INRs outside the range 1.5-4.4'}, {'measure': 'Patients With Dose Changes', 'timeFrame': '12 months', 'description': 'Number of patients with at least one change of maintenance dose during the 12-month study period'}]}, 'oversightModule': {'oversightHasDmc': True}, 'conditionsModule': {'keywords': ['warfarin', 'prothrombin time', 'monitoring'], 'conditions': ['Atrial Fibrillation', 'Heart Valve Diseases', 'Venous Thrombosis']}, 'referencesModule': {'references': [{'pmid': '22084331', 'type': 'DERIVED', 'citation': '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.'}]}, 'descriptionModule': {'briefSummary': '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.\n\nThe investigators hypothesis is that these patients can go less often, e.g. every 12 weeks, for the blood tests.', 'detailedDescription': 'OBJECTIVE: The PRolongation of the INTerval between prothrombin time tests in stable patients (PRINT) is a single center, randomized, double-blind study to demonstrate that testing the prothrombin time every 12 weeks provides the same level of anticoagulant control as conventional testing every 4 weeks in this subset of stable patients. This study will enroll patients who have been treated with vitamin K antagonists (VKA) for at least 6 months and have not had any change to the maintenance dose for the most recent 6 months.\n\nHYPOTHESIS: Our hypothesis is that by extending the interval between tests to 12 weeks in these stable patients, the same level of anticoagulant control, can be maintained. With the large and constantly increasing number of patients on warfarin, a reduced frequency of testing would yield considerable savings for the health care system and a decreased burden for the patient. A review of our anticoagulant clinic revealed that one third of the patients would be eligible for such a prolongation of the test interval.\n\nSTUDY DESIGN: The proposal is a randomized, double-blind, controlled single centre trial performed at Hamilton Health Sciences - General Hospital. Main inclusion criteria are: long-term anticoagulant therapy, managed by our clinic for at least 6 months and with unchanged maintenance dose for at least 6 months. Eligible and consenting patients identified at annual review visits or from the register of patients monitored by the clinic, will be randomized to dosing of warfarin every 4 weeks (control) or every 12 weeks (experimental). All patients will, however, have blood drawn every 4 weeks. Randomization will be performed using a computer-generated randomization sequence. Stratification is done for the two laboratories performing the analysis and for the two therapeutic ranges that patients are to be maintained within, depending on the indication for anticoagulation. Patients with mechanical mitral valve prosthesis are maintained between 2.5 and 3.5, others between 2.0 and 3.0.The randomization sequence will guide the Coordinating and Methods Center to the correct reporting procedure for each patient, and to provide sham INR-values for two out of each set of three 4-weekly tests in the patients allocated to 12-weekly monitoring. Extreme INR results (\\<1.5 or \\>4.4) will always be reported as true results. The investigator and the patient are blind to the procedure and are only aware of the sequence order number.The patients are carefully instructed about risk factors that can change the effect of VKA. They are contacted by telephone after each test for information on the result, the dosing and for questioning of adverse events. After 12 months in the study there is a final visit scheduled at the anticoagulation clinic for review of the patient.\n\nANALYSIS: After the last patient has concluded the study, all clinical data will be transferred to the study statistician for analysis. The primary outcome measure is "the time in therapeutic range" (TTR). The secondary outcome measures are "proportion of patients with extreme INR results", "proportion of INR results that are extreme" and "number of changes of the maintenance dose". These are well-recognized tools for evaluation of the level of anticoagulant control. Major bleeding and objectively verified thromboembolic events will also be registered, but the expected number is very small and not sufficient for any statistical analyses.\n\nSAMPLE SIZE: Sample size calculations are based on 77% TTR for a population with very stable VKA-dose and a maximum tolerable deviation of 7.5 percentage points; one-sided alpha of 2.5% and power of 90%. The sample will accordingly be 107 patients per group. After interim analysis the DSMB recommended to expand the sample size to 125 patients per group (July 16, 2008).'}, 'eligibilityModule': {'sex': 'ALL', 'stdAges': ['ADULT', 'OLDER_ADULT'], 'minimumAge': '18 Years', 'healthyVolunteers': False, 'eligibilityCriteria': 'Inclusion Criteria:\n\n* 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,\n* Anticoagulant therapy managed by the clinic (HHS - General Hospital) for at least 6 months prior to enrolment, and\n* Maintenance dose of warfarin unchanged for the previous 6 months or longer.\n\nExclusion Criteria:\n\n* Age \\<18 years,\n* Life expectancy of less than 1 year,\n* Attending physician believes the patient is not suitable for the study (e.g. psychiatric disorder, history of non-compliance),\n* Geographic inaccessibility or\n* Failure to obtain written consent.'}, 'identificationModule': {'nctId': 'NCT00356759', 'briefTitle': 'Prolongation of the Interval Between Monitoring of Warfarin in Stable Patients', 'organization': {'class': 'OTHER', 'fullName': 'McMaster University'}, 'officialTitle': 'A Randomized Double-blind Study of 4-weekly Versus 12-weekly Monitoring of Stable Patients on Long-term Anticoagulation With Warfarin', 'orgStudyIdInfo': {'id': 'PSI-06-21'}}, 'armsInterventionsModule': {'armGroups': [{'type': 'SHAM_COMPARATOR', 'label': '12-weekly INR', 'description': 'Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times', 'interventionNames': ['Drug: Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times']}, {'type': 'NO_INTERVENTION', 'label': 'Standard management', 'description': 'Dosing warfarin every 4 weeks, all INRs true values'}], 'interventions': [{'name': 'Dosing warfarin every 12 weeks, sham INRs 2 out of 3 times', 'type': 'DRUG', 'otherNames': ['warfarin, Coumadin'], 'description': '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', 'armGroupLabels': ['12-weekly INR']}]}, 'contactsLocationsModule': {'locations': [{'zip': 'L8L 2X2', 'city': 'Hamilton', 'state': 'Ontario', 'country': 'Canada', 'facility': 'HHS - General Hospital, Thrombosis Service', 'geoPoint': {'lat': 43.25011, 'lon': -79.84963}}], 'overallOfficials': [{'name': 'Sam Schulman, Professor', 'role': 'PRINCIPAL_INVESTIGATOR', 'affiliation': 'McMaster University'}]}, 'ipdSharingStatementModule': {'ipdSharing': 'NO'}, 'sponsorCollaboratorsModule': {'leadSponsor': {'name': 'Hamilton Health Sciences Corporation', 'class': 'OTHER'}, 'collaborators': [{'name': "The Physicians' Services Incorporated Foundation", 'class': 'OTHER'}], 'responsibleParty': {'type': 'PRINCIPAL_INVESTIGATOR', 'investigatorTitle': 'Prof.', 'investigatorFullName': 'Sam Schulman', 'investigatorAffiliation': 'McMaster University'}}}}