Prothrombin Times Outside the Therapeutic Range in Otherwise Stable Patients (FORESPEAK-0)
Management of Prothrombin Times Outside the Therapeutic Range in Patients on Warfarin and With Otherwise Stable Levels
Warfarin is very effective for the prevention of blood clots (thrombosis). A test of coagulation, the prothrombin time (PT) is used to monitor the effect. The PT response to warfarin can fluctuate as a result of interactions with a large number of other drugs, food or herbal agents as well as for no apparent reason. Thus, frequent monitoring of the PT and dose adjustments according to the results are required. One third of our patients remain on the same maintenance dose over 6 months. However, also these patients sometimes have a PT result moderately outside the therapeutic range without any obvious explanation. Too short PTs may be due to missed dose(s) or more dark green vegetables in the diet. Too long PTs may be due to a course of antibiotic therapy or less dark green vegetables. Laboratory errors may also occur and can cause deviations in any direction. Most likely, unnoticed fluctuations in the PT occur as well between the time points of monitoring.
There are no guidelines on how to manage the treatment in this situation but there are some typical "behaviours".
Behavior A: Some physicians simply let the patient continue with the same dose. "It is extremely unlikely that the very temporary dose adjustment has any effect on the PT result 4 weeks later and this is a "cosmetic procedure"." Behavior B: Others recommend the patients to take ½ - 1 additional dose in case of short PT and to skip a dose or take half dose in case of long PT, and thereafter to continue with the usual dose. "The investigators need to quickly correct the temporary aberration in order to avoid thrombotic or bleeding complications the next few days.
This may seem like an issue of no importance. The investigators are however performing a series of studies to evaluate if these stable patients can be managed with blood tests less often than every 4 weeks. For that purpose it is important to know how often and why aberrant results occur, the implication and to what extent they can be ignored.
The investigators hypothesis is that in patients with very stable PT-results and unchanged dose for 3 months, should continue with exactly the same maintenance dose, even when the result unexpectedly is slightly above or below the therapeutic range. The investigators believe that most of these occasional PT-results outside the therapeutic range are due to laboratory errors, perhaps missed doses by the patient or temporary change in diet or medications.
研究概览
详细说明
Setting:
Thrombosis Service at HHS - General Hospital. This center monitors the warfarin treatment for 1300 patients in the region. These patient regularly go to a laboratory where they live. Test results (INR-results) are faxed to the Thrombosis Service, which calls the patient the same day to inform them of the results, how to continue dosing the warfarin and when to go for the following blood test.
研究类型
注册 (实际的)
阶段
- 阶段2
联系人和位置
学习地点
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Ontario
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Hamilton、Ontario、加拿大、L8L 2X2
- Thrombosis Service, HHS-General Hospital
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参与标准
资格标准
适合学习的年龄
接受健康志愿者
有资格学习的性别
描述
Inclusion Criteria:
- 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 3 months prior to enrolment, and
- Maintenance dose of warfarin unchanged for the previous 3 months or longer.
- The INR result is outside the therapeutic range as follows:
For those with target 2.0-3.0: Either an INR of 1.5-1.9 or an INR of 3.1-4.4. For those with target 2.5-3.5: Either an INR of 1.5-2.4 or an INR of 3.6-4.4.
Exclusion Criteria:
- Age <18 years,
- Long-term (>1 week) change in any other medication
- Long-term (>1 week) change in diet, especially regarding green vegetables.
- Attending physician believes the patient is not suitable for the study (e.g. psychiatric disorder, history of non-compliance),
- Failure to obtain telephone consent.
学习计划
研究是如何设计的?
设计细节
- 主要用途:治疗
- 分配:随机化
- 介入模型:并行分配
- 屏蔽:无(打开标签)
武器和干预
参与者组/臂 |
干预/治疗 |
---|---|
实验性的:No change
Intervention Drug warfarin no change in the dose is performed
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No change: Continue without any change in spite of prothrombin time outside the therapeutic range.
其他名称:
Change: Increase one dose in case prothrombin time is below the therapeutic range; delete or reduce one dose in case prothrombin time is above the therapeutic range.
其他名称:
|
有源比较器:Change
Intervention Drug Warfarin One dose increased if subtherapeutic level; one dose deleted or reduced if supratherapeutic level
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No change: Continue without any change in spite of prothrombin time outside the therapeutic range.
其他名称:
Change: Increase one dose in case prothrombin time is below the therapeutic range; delete or reduce one dose in case prothrombin time is above the therapeutic range.
其他名称:
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研究衡量的是什么?
主要结果指标
结果测量 |
措施说明 |
大体时间 |
---|---|---|
Number of Patients With Prothrombin Time Results Within the Therapeutic Range After 2 Weeks
大体时间:2 weeks
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The number of patients with "follow-up INRs" within the therapeutic range was compared for patients with a single dose skipped/reduced/added versus patients with no change of dose.
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2 weeks
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合作者和调查者
出版物和有用的链接
研究记录日期
研究主要日期
学习开始
初级完成 (实际的)
研究完成 (实际的)
研究注册日期
首次提交
首先提交符合 QC 标准的
首次发布 (估计)
研究记录更新
最后更新发布 (估计)
上次提交的符合 QC 标准的更新
最后验证
更多信息
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