心脏机械瓣膜置换术后华法林抗凝治疗效果及INR抗凝强度范围分析

目的探讨华法林抗凝在心脏机械瓣膜置换术后的治疗效果及抗凝强度的范围。方法选取行心脏机械瓣膜置换术患者72例,按随机数字表法分成对照组和观察组各36例。对照组华法林服用剂量按INR值范围2.0～3.0调整,观察组华法林服用剂量按INR值范围1.5～2.0调整。对比两组治疗后并发症发生率及各项心功能指标。结果治疗后,两组血栓栓塞事件发生率相比,差异无统计学意义(P>0.05);但观察组出血事件发生率低于对照组,差异有统计学意义(P<0.05);观察组PT、TT、APTT水平均高于对照组,FIB水平低于对照组,差异有统计学意义(P<0.05)。结论心脏机械瓣膜置换术后华法林INR抗凝强度的范围1.5-2.0更安全可靠,预后良好,可有效降低并发症发生率。     

基层心脏瓣膜置换术后华法林抗凝治疗15例分析

目的探讨基层心脏瓣膜置换术后抗凝治疗的效果、安全和影响因素。方法本组15例,年龄18～46岁,常规服用华法林,根据INR值调整量,观察患者INR值、栓塞、出血事件等情况,随访3a。结果男性INR值(1.82±0.67),女性INR值(1.79±0.64),皮肤、黏膜出血和牙龈出血各1例,血尿2例,其余患者未见出血和栓塞倾向。结论基层医院加强心脏瓣膜置换术后患者抗凝治疗的监测和指导,规范抗凝治疗,减少出血和血栓并发症,提高患者的生命质量。     

198例心脏机械瓣膜置换术患者口服华法林的临床监测及护理

目的研究心脏机械瓣膜置换术后口服华法林患者血浆凝血酶原前体蛋白(prothrombin precursor protein,PIVKA-Ⅱ)、凝血酶原时间(prothrombintime,PT)、国际标准化比率(international normalized rate,INR)的变化及其临床意义。方法 198例心脏机械瓣膜置换术后口服华法林患者为病例组,30例门诊体检人员为健康对照组,分别进行血浆PIVKA-Ⅱ、PT、INR测定。结果研究组首次服华法林后8h后,血浆PIVKA-Ⅱ浓度即显著增高,差异有统计学意义(P0.05);首次服华法林24h后,PT、INR显著增高,差异有统计学意义(P0.05)。抗凝后多数患者有不同程度的出血,其中2例出现腰大肌血肿,3例出现脑出血,1例出现脑血栓,经手术治疗、药物调整及护理后均康复。结论上述指标能较客观地反映心脏机械瓣膜置换术后口服华法林患者的病理变化过程。对患者进行心理治疗等护理可以提高治疗效果、减少并发症。     

心房颤动患者应用华法林抗凝治疗的护理体会

目的 总结对心房颤动（房颤）患者应用华法林抗凝治疗的用药指导和护理体会。方法 96例房颤患者应用华法林抗凝治疗，服用前强化健康教育，服用期间监测凝血酶原时间（PT）及其国际标准化比率（INR），观察其抗凝效果及主要不良反应。结果 经过正规的抗凝治疗和护理，未出现血栓栓塞事件发生，2例患者出现轻微皮下出血，经调整华法林剂量后出血停止，无严重出血发生。结论 服用华法林的房颤患者应定期监测PT及INR。早期发现出血的征象并加强健康教育，可避免严重并发症的发生。     

心脏瓣膜置换术后抗凝治疗发生栓塞12例分析

目的：探讨机械瓣膜置换术后发生栓塞的原因以及预防措施。方法：分析12例患者临床资料及用药特点。结果：心脏瓣膜置换术后患者均需华法林抗凝治疗,严密监测凝血指标。结论：我国人工机械瓣膜置换术患者的抗凝强度应控制在INR 1.3-2.3（AVR1.3-1.8;MVR DVR：1.8-2.3,可以减少口服抗凝治疗的并发症,获得满意的预防血栓栓塞,减少与抗凝有关的出血的效果。     

心脏瓣膜置换术后影响华法林抗凝疗效的人口学因素分析

目的:探讨影响心脏瓣膜置换术后患者华法林维持剂量的人口学因素,以指导术后的抗凝治疗.方法:收集852例心脏瓣膜置换术后使用华法林抗凝治疗的患者资料,分别将华法林维持剂量与性别、年龄、体表面积、吸烟、饮酒等因素进行相关性分析,采用逐步回归方法分析这些人口学因素对华法维持剂量的影响.结果:(1)女性患者华法林的维持剂量和 PT-INR(凝血酶原国际标准化比值)都要比男性患者小.(2)华法林维持剂量与年龄呈负相关(r=0.250,P<0.001),与体表面积呈正相关(r=0.337,P<0.001).(3)年龄和体表面积可以解释华法林维持剂量个体异的17.9%.结论:本研究证实一些人口学因素例如年龄和体表面积可以解释华法林维持剂量的部分个体差异,接下来还需进一步地探讨其他因素,例如遗传因素对华法林剂量的影响.     

老年持续性心房颤动患者应用华法林抗凝治疗国际标准化比值安全范围的探讨

目的探讨老年持续性心房颤动患者应用华法林抗凝治疗的有效性、安全性及国际标准化比值（INR）范围.方法老年持续性心房颤动患者服用华法林抗凝治疗69例,观察华法林达标时间、维持剂量、安全的INR范围及不良反应.结果华法林达标时间及维持剂量虽有个体差异,但多数（88%）患者在15～30 d内以1.5～2.25 mg/d的量使INR稳定于1.8～2.5,出血发生率最低.结论老年持续性心房颤动患者应用华法林抗凝治疗时,使INR稳定于1.8～2.5既有效又安全.     

心脏瓣膜置换术后服用华法林抗凝治疗的临床观察

目的：对86例心脏瓣膜置换术后病人进行抗凝治疗，旨在了解病人术后服用华法林剂量及并发症情况。方法：本组86例患者，均在常规体外循环及心肌保护下施术，术后第1日晚开始服用华法林，首剂3～5mg，每日晨查血浆凝血酶原时间(PT)及国际标准化比值(INR)，维持PT为20～30秒，INR为1．8～2．4。结果：全组86例病人查INR值1118例次，其中INR 1．0～1．7者220例次，栓塞2例次1人，栓塞率1．2％；INR 1．8～2．4者785例次，无出血及栓塞；INR 2．5～4．0者108例次，出血21例次8人，出血率9．3％；INR 4．1～5．5者5例次，出血5例次4人，出血率4．7％。结论：心脏瓣膜置换术后须终生抗凝治疗。与之有关的出血或栓塞是换瓣术后常见并严重的并发症，因此正确的术后抗凝治疗对于减少并发症，提高病人术后生存率具有决定性的意义。     

心脏机械瓣膜置换术后输尿管中下段结石的手术及围术期处理

探讨心脏机械瓣膜置换术后输尿管中下段结石的手术方法选择及围手术期抗凝药物的使用及其安全性。【方法】8例心脏机械瓣膜置换术后罹患输尿管中下段结石患者,长期口服华法林抗凝治疗,入院后停用华法林,改用普通肝素0．5 mg／kg ,q4 h 静脉注射,调整凝血酶原时间（PT ）至正常范围之内,于手术前24 h 停用抗凝药物。手术方式采用全麻下输尿管硬镜气压弹道碎石加 D‐J 管内置术,手术时间控制在30 min 之内,术后24～48 h 口服华法林并与肝素重叠使用,3 d 后停用肝素,单服华法林并维持国际标准化比率（INR）于治疗范围之内。【结果】8例患者均顺利渡过围术期,一次性碎石排石率100％。【结论】针对心脏机械瓣膜置换术后输尿管中下段结石患者,在合理调整抗凝药物种类、剂量及用法,掌握合适的抗凝强度,并注意术中操作及术后处理的前提条件下,输尿管镜碎石＋ D‐J 管内置术,其疗效确,安全可靠。     

心脏瓣膜置换术后患者华法林抗凝治疗依从性影响因素分析及对策

目的：探讨心脏瓣膜置换术后患者华法林抗凝治疗依从性的影响因素分析及对策。方法：选取2021年1月1日～2022年3月31日行心脏瓣膜置换术的209例患者作为研究对象，分为达标组(INR达标率≥80%)138例和未达标组(INR达标率<80%)71例，术后均给予华法林抗凝治疗，分析影响患者华法林抗凝治疗依从性的相关因素。结果：华法林抗凝知识认知程度调查结果显示，华法林的用法、华法林口服时间及华法林的效用认知正确率均高于80%。两组受教育程度、居住地、家庭收入、华法林抗凝知识认知程度比较差异有统计学意义(P<0.05)。多元Logistic回归分析结果显示，受教育程度、居住地、华法林抗凝知识认知程度为影响患者心脏瓣膜置换术后依从性的独立危险因素(P<0.05)。结论：心脏瓣膜置换术后患者华法林抗凝知识总体认知水平不高，且依从性较差，其中受教育程度低、居住地为农村、华法林抗凝知识认知程度差均为导致患者依从性差的独立危险因素，临床需加强对患者的干预，以提高术后治疗依从性。     

机械瓣置换术后患者目标INR1.60~2.20及以每周为单位华法林剂量调整合理性的初步评价

目的评价机械瓣置换术后患者目标国际标准化比值(international normalized ratio,INR)1.60~2.20及以每周为单位华法林剂量调整的合理性。方法连续收集2011年7月至2013年2月在四川大学华西医院门诊随访的机械瓣置换手术后≥6个月的患者资料,患者目标INR控制在1.60~2.20内,当INR值超出目标范围或可接受范围时,进行以每周为单位的华法林剂量调整。采用血栓形成、栓塞及出血、应用治疗范围时间(TTR)及治疗范围时间分数(FTTR)来评价抗凝治疗的效果。结果共纳入患者1442例,共检测INR6 461份。患者年龄14~80岁(48.2±10.6岁),其中女性1043例(72.3%),男性399例(27.7%),术后随访6~180月(39.2±37.4月)。INR检测值为0.90~8.39(1.85±0.49),每周达可接受的INR(1.50~2.30)所需华法林剂量为2.50~61.25 mg(20.89±6.93mg)。目标INR及可接受INR范围的TTR分别为51.1%(156640.5天/306415.0天)和64.9%(198856.0天/306415.0天);目标INR及可接受INR范围的FTTR分别为49.4%(3193次/6461次)和62.6%(4047次/6461次)。本研究1443例患者在20个月随访期内出现的抗凝相关并发症包括左房血栓形成2例,脑梗塞2例(1例完全恢复,1例肢体活动障碍);严重出血8例,其中脑溢血3例(1例死亡,2例完全恢复),消化道出血3例,肺癌咳血1例,子宫出血1例(手术切除子宫);非严重出血7例(皮下淤斑或青紫)。结论机械瓣置换术后患者以INR 1.60~2.20为目标并采用以每周为单位的华法林剂量调整是合理的。     

Long-term treatment with warfarin in Chinese population

OBJECTIVE: To estimate the incidence of and risks for bleeding and thromboembolic events after warfarin anticoagulation. We also explored the dosage and international normalized ratio (INR) among Chinese patients during long-term warfarin therapy. METHODS: The population in this retrospective study consisted of inpatients of the only medical center for northern Taipei City, whose initial course of warfarin therapy continued for more than four weeks. Enrollment began in June 1995 and ended in February 1996. Follow-up was completed in March 1998. Relevant data were collected by chart review. The rate of events was calculated using the Kaplan-Meier method, and risk factors were identified by the Cox proportional hazard model. RESULTS: During the study period, 226 patients were identified. The total follow-up time was 248.7 patient-years. Sixty-one patients (27.0%) received anticoagulation for mechanical prosthetic valve, but their duration of therapy accounted for 48.6% of the total patient-years of follow-up. The starting dosage (mean +/- SD) was 3.4+/-1.4 mg/d (range 1.3-10); the maintenance dosage was 3.1+/-1.2 mg/d (range 1.2-7.7). There were 1060 dosing adjustments and 3398 INR measurements collected for these patients. The independent determinants of maintenance dosage were age, body weight, and indication of mechanical prosthetic valve. The INR was 1.9+/-0.5 (range 1.0-3.7). The cumulative probabilities for hemorrhage at 12, 24, and 34 months were 24.5%, 32.3%, and 38.4%, respectively. The corresponding figures for thromboembolism were 8.5%, 10.7%, and 10.7%, respectively. Three hemorrhages were fatal. After adjusting for other patient characteristics, increasing age was the only independent risk factor identified for bleeding. CONCLUSIONS: Antithrombotic efficacy seemed to be maintained, although the mean INR was 1.9. Even so, the substantial incidence of bleeding, especially fatal bleeding, remains a concern. Low-intensity anticoagulation might be needed for Chinese patients during long-term warfarin therapy.     

Effects of therapeutic plasma exchange on anticoagulants in patients receiving therapeutic anticoagulation: a systematic review

Therapeutic plasma exchange (TPE) removes coagulation proteins, but its impact on therapeutic anticoagulation is unknown. We performed a systematic review of the literature to determine the coagulation effects of TPE in patients receiving systemic anticoagulation. We searched MEDLINE, CINAHL, EMBASE, and Web of Science until June 2018 for studies combining controlled vocabulary and keywords related to therapeutic plasma exchange, plasmapheresis, anticoagulants, and therapy. The primary outcome was the effect of TPE on anti‐Xa activity, activated partial thromboplastin time (aPTT), or international normalized ratio (INR). The secondary outcome was reports of post‐TPE bleeding or thrombosis. A total of 1830 references were screened and eight studies identified. Our selected studies (five case reports and three case series) involved 23 patients and evaluated the effects of seven anticoagulants. Six studies of unfractionated heparin, low‐molecular‐weight heparins, and direct oral anticoagulants demonstrated an anti‐Xa level decline. Two studies of unfractionated heparin and low‐molecular‐weight heparins showed an aPTT increase. One study of warfarin showed a post‐TPE INR increase. Reports of post‐TPE bleeding occurred in two patients and thrombosis in one. In patients receiving therapeutic anticoagulation, TPE is associated with anti‐Xa activity decline and aPTT and INR increase. These coagulation changes do not appear to significantly increase bleeding or thrombotic risk. Our data suggest the need for prospective studies to investigate the true clinical impact of TPE on therapeutic anticoagulation.     

Factors affecting warfarin therapy following cardiac valve surgery

OBJECTIVE: To determine the factors that affect the initial response to warfarin therapy in Korean patients after cardiac valve surgery. METHODS: A retrospective analysis of 127 patients who had undergone cardiac valve surgery at Seoul National University Hospital was performed. On the first day, most patients received warfarin 5 mg, while some received an individualized warfarin dose according to their physician's decision. Doses to be given on the following days were determined based on daily international normalized ratio (INR) and the previous doses. To measure warfarin sensitivity, the warfarin dose index (WDI), defined as the INR divided by the mean warfarin dose administered during the preceding 3 days, was introduced. The effects of age, gender, weight, serum albumin concentration, baseline INR, cardiopulmonary bypass time, and concurrent administration of amiodarone were evaluated. RESULTS: The patients' weight, initial serum albumin concentration, and baseline INR value influenced their initial response to warfarin. The initial WDI correlated negatively with the initial serum albumin concentration (p < 0.001) and body weight (p < 0.05) and positively with the baseline INR (p < 0.01). The initial WDI of the patients taking amiodarone was significantly higher (mean +/- SD 0.74 +/- 0.34) than that of patients without amiodarone (0.46 +/- 0.22) (p < 0.001). Maintenance doses correlated negatively with the initial warfarin response (p < 0.001) and positively with body weight (p = 0.053). CONCLUSIONS: The factors associated with an increased initial warfarin response in patients after cardiac valve surgery were high baseline INR, low postoperative serum albumin concentration, and concurrent administration of amiodarone. Thus, patients with any of these factors should receive a smaller initial warfarin dose. Also, to predict the warfarin maintenance dose from the initial response, the effect of transient changes in the sensitivity to warfarin during the initial period should be considered.     

Increased sensitivity to warfarin after heart valve replacement

BACKGROUND: The dosage requirement of warfarin to achieve a given international normalized ratio (INR) often varies considerably between the immediate postoperative period and long-term follow-up in patients with prosthetic heart valves, leading to INR instability. OBJECTIVE: To document the extent of warfarin sensitivity in a prospective study of patients receiving heart valve replacements. METHODS: Clinical and laboratory data regarding anticoagulation for 111 patients who received warfarin following heart valve replacement were collected during their hospital stay (induction period) and between 1 and 3 months after surgery (follow-up period). RESULTS: Mean patient age was 65.39 +/- 10.55 years (range 29-85), with 66 men. The mean INR value during the follow-up period was, on average, 0.21 higher than the induction period (2.81 +/- 0.5 vs 2.6 +/- 0.6; p = 0.007). The mean follow-up warfarin dose was 1.54 mg higher than the mean induction warfarin dose (5.09 +/- 2.03 vs 3.55 +/- 1.94 mg; p < 0.001). The warfarin dose index, which indicates relative sensitivity of warfarin, decreased from 1.16 to 0.65 (p < 0.001). Although the INR values during the induction and follow-up periods were similar, the dose requirement in the follow-up period was, on average, 43% higher than that of the induction period. CONCLUSIONS: Immediately after heart valve replacement, patients are more sensitive to warfarin and should receive a lower warfarin dose during the initial phase of oral anticoagulation treatment. This enhanced sensitivity decreases with time. Patients require frequent monitoring and are likely to need an increase in the warfarin dose to avoid insufficient anticoagulation during the early follow-up period.     

华法林治疗急性下肢深静脉血栓形成患者凝血酶原-国际标准化比值国人适宜性有效值的初步探讨

目的 初步探讨华法林治疗急性期下肢深静脉血栓形成(DVT)患者适宜国人的凝血酶原-国际标准化比值(PT-INR).方法 选择具有华法林抗凝治疗适应证的DVT患者87例,随机分为A、B 2组,A组(47例)应用华法林,调整PT-INR在1.7～2.5,B组(40例)应用华法林,调整PT-INR在2.0～3.0,比较华法林治疗的有效性及出血并发症的发生率.结果 A组47例患者,46例肢体肿胀明显减退消失,1例无效,经彩超、GT及肿瘤标志物检查,考虑为盆腔肿瘤,有效率为98%;全部患者无明显出血症状.B组40例患者,38例肢体肿胀明显减退消失,2例症状好转不明显,其中Cockett综合征1例,另一例原因不明,有效率为95%;3例出现轻度牙龈及鼻黏膜出血,1例出现胃肠道内出血.2组无肺栓塞发生.结论 国人急性DVT治疗中PT-INR调整在1.7～2.5同样有效,且出血等并发症明显减少.

Abstract：

Objective To explore the suitable range of PT-INR for Chinese people with acute deep venous thrombosis (DVT) treated by warfarin anticoagulation therapy. Methods Eighty seven DVT patients with indications to warfarin anticoagulation therapy were enrolled into the study and divide into two groups randomly. Patients from group A (n=47) took warfarin to adjust the PT-INR to range 1.7-2. 5,and patients from group B (n =40) took warfarin to adjust the PT-INR to range 2. 0-3. 0. The therapeutic effectiveness and the incidence of bleeding complications were compared between two groups. Results Forty-six patients (46/47,98%) had limb swelling symptoms relief in group A with one exception,which was diagnosed as pelvic tumor by ultrasonography,CT and tumor markers examination later. No patient underwent bleeding in group A Thirty eight patients (38/40,93%) had limb swelling symptoms relief in group group B with two exceptions,of which one case had Cockett syndrome and the other one had unknown aetiology. The total effective rate of group B was 95% . As to the complications of this group,3 patients had slight gum and nasal mucous membrane bleeding, 1 patient developed gastrointestinal bleeding. No patients had pulmonary embolism in both groups. Conclusion For Chinese people,anticoagulation therapy of acute deep venous thrombosis to adjust the range of PT-INR to 1.7-2. 5, shows good effectiveness and significantly reduced bleeding complications.     

A randomized clinical trial of high-intensity warfarin vs. conventional antithrombotic therapy for the prevention of recurrent thrombosis in patients with the antiphospholipid syndrome (WAPS).

BACKGROUND: The optimal intensity of oral anticoagulation for the prevention of recurrent thrombosis in patients with antiphospholipid antibody syndrome is uncertain. Retrospective studies show that only high-intensity oral anticoagulation [target international normalized ratio (INR) >3.0] is effective but a recent randomized clinical trial comparing high (INR range 3.0-4.0) vs. moderate (INR 2.0-3.0) intensities of anticoagulation failed to confirm this assumption. METHODS: We conducted a randomized trial in which 109 patients with antiphospholipid syndrome (APS) and previous thrombosis were given either high-intensity warfarin (INR range 3.0-4.5, 54 patients) or standard antithrombotic therapy (warfarin, INR range 2.0-3.0 in 52 patients or aspirin alone, 100 mg day(-1) in three patients) to determine whether intensive anticoagulation is superior to standard treatment in preventing symptomatic thromboembolism without increasing the bleeding risk. RESULTS: The 109 patients enrolled in the trial were followed up for a median time of 3.6 years. Mean INR during follow-up was 3.2 (SD 0.6) in the high-intensity warfarin group and 2.5 (SD 0.3) (P < 0.0001) in the conventional treatment patients given warfarin. Recurrent thrombosis was observed in six of 54 patients (11.1%) assigned to receive high-intensity warfarin and in three of 55 patients (5.5%) assigned to receive conventional treatment [hazard ratio for the high intensity group, 1.97; 95% confidence interval (CI) 0.49-7.89]. Major and minor bleeding occurred in 15 patients (two major) (27.8%) assigned to receive high-intensity warfarin and eight (three major) (14.6%) assigned to receive conventional treatment (hazard ratio 2.18; 95% CI 0.92-5.15). CONCLUSIONS: High-intensity warfarin was not superior to standard treatment in preventing recurrent thrombosis in patients with APS and was associated with an increased rate of minor hemorrhagic complications.     

机械瓣膜置换术后远期抗凝状态观察及临床意义

目的 了解机械心脏瓣膜置换术后远期国际标准化比值(INR)与并发症的关系,最佳抗凝强度范围及临床意义.方法 对行机械心脏瓣膜置换术后出院6个月以上的患者在门诊检查凝血三项(PT、PT%、PTR、INR、Fbg、APTY)216例次.按照INR结果不同分为4组.Ⅰ组:INR<1.5;Ⅱ组:INR 1.5～2.0;Ⅲ组:INR 2.1～2.5;Ⅳ组:INR>2.5.结果 Ⅰ组28例次,华法林服用量(3.61±1.44)mg,INR(1.38±0.12),出现脑栓塞4例次,并发症发生率14%;Ⅱ组92例次,华法林服用量(3.50±1.37)mg,INR(1.65±0.14),出现鼻出血2例次,并发症发生率2%;Ⅲ组80例次,华法林服用量(3.18±1.63)mg,INR(2.23±0.19),出现血尿2例次,鼻出血2例次,并发症发生率5%;Ⅳ组16例次,华法林服用量(2.32±1.23)mg,INR(2.80±0.19),出现鼻出血2例次、咯血1例次,并发症发生率18.7%.Ⅱ、Ⅲ组的并发症占总数的79.6%,INR在1.5～2.5之间并发症最低.结论 INR在1.5～2.5之间是安全可靠的,是本地区最佳抗凝强度范围.机械心脏瓣膜置换术后抗凝强度是动态的,术后远期更应高度关注抗凝状态.     

Search for predictors of nontherapeutic INR results with warfarin therapy

BACKGROUND: The effectiveness and safety of warfarin require maintaining an international normalized ratio (INR) within the therapeutic range. OBJECTIVE: To identify predictors of nontherapeutic INR results in patients receiving warfarin. METHODS: A retrospective study was conducted using 350 ambulatory care patients from a broad geographic region, all receiving long-term warfarin therapy and followed in a tertiary-care cardiology clinic. Possible predictors of nontherapeutic INR results (gender, age, body weight, body mass index, height, race, tobacco use, alcohol use, warfarin dose, therapeutic indication, regimen intensity, INR monitoring frequency/category, interacting medications, adverse events) were assessed with logistic regression models. Subset analysis involved 146 patients concurrently monitored with capillary whole blood INR (CoaguChek). RESULTS: As measured on venous specimens, 52% (182/350) of the patients had subtherapeutic INR results and 13% (44/350) had supratherapeutic INR results despite frequent (< or =4 wk) monitoring in 75% of the patients. Due to the small sample size, supratherapeutic INR results could not be further analyzed. Of 19 predictors tested, only daily warfarin dose (p < 0.02) and regimen intensity (p < 0.03) were significant independent and additive predictors of subtherapeutic results. Patients on the high-intensity regimen (INR 2.5-3.5) and receiving warfarin < or =6 mg/day had >50% risk of having subtherapeutic INR results. Subtherapeutic CoaguChek results were independent predictors of subtherapeutic venipuncture INR results in the subset (p = 0.001). CONCLUSIONS: In the absence of readily identifiable predictors, only higher warfarin dosing and/or more frequent monitoring (possibly with point-of-care/home monitoring devices) may minimize the time that INRs are subtherapeutic, especially in patients receiving low-dose and/or high-intensity anticoagulation therapy.