Oral Warfarin Therapy Research Articles

Non‐vitamin K Oral Anticoagulants Versus Warfarin for Patients with Atrial Fibrillation: Absolute Benefit and Harm Assessments Yield Novel Insights

Benefits and/or harms (including costs) of non-vitamin K oral anticoagulants (NOACs) versus warfarin therapy need appreciation in relative and absolute terms. Accordingly, we derived clinically relevant relative and absolute benefit/harm parameters for NOACs (apixaban, dabigatran, rivaroxaban, edoxaban) compared to warfarin from four clinical trials involving atrial fibrillation (AF) patients. For each trial, we tabulated patient numbers enduring four important outcomes and calculated unadjusted relative risk reduction (RRR) and number needed to treat (NNT)/year values (and 95% confidence intervals) for the NAOC compared to warfarin. These outcomes were as follows: stroke/systemic embolism (primary endpoint), hemorrhagic stroke, major bleeds, and death. We also addressed drug acquisition costs. Each NOAC was noninferior to warfarin for primary-outcome prevention; RRRs were 12-33% and NNT/year values were 182-481, and all but one indicated statistically significant superiority. All the NOACs yielded statistically significant reductions in hemorrhagic stroke risk; RRRs were 42-74% and NNT/year values were 364-528. Major bleeding risk was comparable in both groups. Apixaban yielded a lower NNT/year for preventing death than for primary-outcome prevention. Compared to warfarin, NOAC acquisition costs were 70- to 140-fold greater. For the primary outcome, the absolute benefits of NOACs were modest (NNT/year values being large). Reduced hemorrhagic stroke rates with NOACs could be due to superior embolic infarct prevention and fewer consequential hemorrhagic transformations. Among apixaban recipients, the absolute mortality benefit exceeded that for the primary outcome, indicating prevention of additional unrelated deaths. The substantially greater NOAC acquisition costs need viewing against probable greater safety and the avoidance of monitoring bleeding risks.

Direct-Acting Oral Anticoagulants: Practical Considerations for Emergency Medicine Physicians.

Nonvalvular atrial fibrillation- (NVAF-) related stroke and venous thromboembolism (VTE) are cardiovascular diseases associated with significant morbidity and economic burden. The historical standard treatment of VTE has been the administration of parenteral heparinoid until oral warfarin therapy attains a therapeutic international normalized ratio. Warfarin has been the most common medication for stroke prevention in NVAF. Warfarin use is complicated by a narrow therapeutic window, unpredictable dose response, numerous food and drug interactions, and requirements for frequent monitoring. To overcome these disadvantages, direct-acting oral anticoagulants (DOACs)—dabigatran, rivaroxaban, apixaban, and edoxaban—have been developed for the prevention of stroke or systemic embolic events (SEE) in patients with NVAF and for the treatment of VTE. Advantages of DOACs include predictable pharmacokinetics, few drug-drug interactions, and low monitoring requirements. In clinical studies, DOACs are noninferior to warfarin for the prevention of NVAF-related stroke and the treatment and prevention of VTE as well as postoperative knee and hip surgery VTE prophylaxis, with decreased bleeding risks. This review addresses the practical considerations for the emergency physician in DOAC use, including dosing recommendations, laboratory monitoring, anticoagulation reversal, and cost-effectiveness. The challenges of DOACs, such as the lack of specific laboratory measurements and antidotes, are also discussed.

Protocol for Cerebral Microbleeds during the Non–Vitamin K Antagonist Oral Anticoagulants or Warfarin Therapy in Stroke Patients with Nonvalvular Atrial Fibrillation (CMB-NOW) Study: Multisite Pilot Trial

Anticoagulants are widely used to prevent recurrence of ischemic stroke in patients with nonvalvular atrial fibrillation, but in some patients, they also cause bleeding, particularly intracranial hemorrhage. One of the independent predictors of intracerebral hemorrhage is the presence of cerebral microbleeds (CMBs); a high incidence of intracerebral hemorrhage is reported in warfarin-treated patients with multiple CMBs. Longitudinal study suggested that the presence of CMBs at baseline is a predictor of new CMBs in warfarin-treated patients. However, there has been no study on the progression of CMBs in patients receiving the non-vitamin K antagonist oral anticoagulants (NOACs). This study tests the hypothesis that the incidence of hemorrhagic stroke is lower in patients receiving NOACs (dabigatran,rivaroxaban, apixaban, and edoxaban) than in those receiving warfarin, and this difference reflects the difference in the effects of warfarin and NOACs on the progression of CMBs. We will enroll 200 patients with at least 1 CMB detected by 1.5T magnetic resonance imaging (T2(∗)-weighted imaging) at baseline and who have received NOACs or warfarin for at least 12months. Primary end point is the proportion of subjects with an increased number of CMBs at month 12 of treatment with NOACs or warfarin. If the results of this study support the efficacy of NOACs for preventing increase of CMBs, this would be of great interest to domestic and overseas clinicians, in view of the potential therapeutic impact, including that on primary prevention of ischemic stroke.

Anticoagulant management of pregnant women with mechanical heart valve replacement during perioperative period.

To investigate the morbidity of complications and pregnancy outcomes in women with mechanical heart valve replacement who received low-dose oral anticoagulation treatment with warfarin throughout the pregnancy, compare the prognosis and complications of patients who were treated with single oral warfarin treatment or the "bridging" therapy treatment, investigate the influence of using vitamin K1 before emergency cesarean section delivery on postoperative warfarin anticoagulant effect and to explore an appropriate anticoagulant regimen during perioperative period for pregnant women with mechanical heart valve replacement. 46 pregnant women with mechanical heart valve replacement who received low-dose oral anticoagulation treatment from October 2008 to October 2014 treated at West China Women's and Children's Hospital were retrospectively reviewed. Eight patients received emergency cesarean section (CS), while 38 patients received selective CS, in which 17 patients received single oral warfarin and 21 patients received "bridging" anticoagulation treatment during postoperative period. Morbidity of complications and the time to achieve the target INR after operation were compared. The mechanical valves were at the mitral position in 35 (76.09 %) patients, at the aortic position in 2 (4.35 %) patient and at both the mitral and aortic position in 9 (19.57 %) patients. 46 full-term healthy babies were delivered and no maternal thromboembolic was observed during pregnancy. There was no significant difference of the amount of uterine bleeding between single oral warfarin group and "bridging" treatment group during postpartum period. In single oral warfarin group, one valve thrombosis was observed and led to sudden death. No periphery thrombosis, hematoma, general hemorrhage or other sign of over-anticoagulation was observed. The INR increased more slowly in the group who received emergency CS with preoperative application of vitamin K1 than other two groups. The use of vitamin K1 preoperatively might result in warfarin resistance and discontinuation of warfarin therapy before selective CS might be more appropriate than application of vitamin K1. The "bridging" anticoagulation treatment which combines oral warfarin and subcutaneous LMWH might be more effective and safer than single oral warfarin therapy for patients with mechanical heart valve replacement during postoperative period, no matter selective or emergency CS. The safety of low-dose oral warfarin therapy throughout pregnancy is still under controversy.

Peribulbar versus sub-Tenon block in cardiac patients undergoing cataract surgery during warfarin therapy

ObjectiveTo compare sub-Tenon’s block with peribulbar block in patients on oral warfarin therapy undergoing cataract surgery.Materials and methodsWe studied 100 patients on warfarin undergoing cataract surgery; randomly allocated into one of two groups; sub-Tenon’s group (group S, n = 50), and peribulbar group (group P, n = 50). In group (S), sub-Tenon’s injection of 3–5 ml of anesthetic agent was done using a 25 mm sub-Tenon’s cannula. In group (P), the peribulbar block with 3–4 ml of 2% lidocaine–hyaluronidase (10 IU/ml) and 0.5% bupivacaine was done. Pain and akinesia and postoperative complications were assessed.ResultsSub-Tenon group showed significantly higher frequency of hemorrhage compared to peribulbar group (30% versus 8%, p = 0.041), mainly of grade I. The two groups had comparable frequency of subconjunctival hemorrhage (p = 1.000). No patients experienced sight-threatening hemorrhagic complications. Pain was significantly lower in the sub-Tenon group. Akinesia was significantly better (p = 0.025) 2 min after injection and comparable from 4 to 10 min after injection in the peribulbar group. The majority of patients in the two groups reported satisfaction (p = 0.372). The surgeon expressed higher satisfaction with peribulbar block (94%) compared to sub-Tenon’s block (81%) (p = 0.064).ConclusionPeribulbar and sub-Tenon techniques were relatively safe in patients on anticoagulants during cataract operation. We recommend peribulbar technique owing to significantly less bleeding and more satisfactory akinesia response and hence surgeon comfort.

Abdominal aortic thrombosis in a young male patient living with human immuno deficiency virus/acquired immune deficiency syndrome

Background: Thrombotic event in Acquired Immune Deficiency Syndrome (AIDS) patients was a rare clinical entity prior to Highly Active Anti Retro Viral Therapy (HAART) era, but it is increasing. Aortic thrombosis, a rare fatal event, leads to arterial embolic events often due to thrombi associated with extensive underlying atherosclerosis. Case Presentation: We report a case of young male suffering from AIDS, presented with chronic diarrhea and abdominal pain. Patient was diagnosed as a case of partial abdominal aortic thrombosis. No familial predisposition or any other risk factor for thrombosis was identified. Treatment following intravenous heparin was started and later on switched to oral warfarin. After 10 days, he was devoid of symptoms and discharged on oral warfarin and Anti-Retro Viral Therapy (ART). Discussion: The current case report reinforces that similar situations are bound to arise again in the future. Clinicians should also consider etiologies other than infectious as cause of abdominal pain to prevent any catastrophe. Clinicians should be aware and alert of unprovoked thrombosis to promote timely treatment and prophylaxis.

A vertebral artery dissection with basilar artery occlusion in a child.

This paper presents the case report of an 11-year-old boy with an acute dissection with thrombosis of the left vertebral artery and thrombosis of the basilar artery. The patient was treated with acute systemic thrombolysis, followed by intra-arterial thrombolysis, without any clinical improvement, showing left hemiplegia, bilateral clonus, hyperreflexia, and impaired consciousness. MRI indicated persistent thrombosis of the arteria basilaris with edema and ischemia of the right brainstem. Heparinization for 72 hours, followed by a two-week LMWH treatment and subsequent oral warfarin therapy, resulted in a lasting improvement of the symptoms. Vertebral artery dissection after minor trauma is rare in children. While acute basilar artery occlusion as a complication is even more infrequent, it is potentially fatal, which means that prompt diagnosis and treatment are imperative. The lack of class I recommendation guidelines for children regarding treatment of vertebral artery dissection and basilar artery occlusion means that initial and follow-up management both require a multidisciplinary approach to coordinate emergency, critical care, interventional radiology, and child neurology services.

Variability of warfarin dose response associated with CYP2C9 and VKORC1 gene polymorphisms in Chinese patients

To investigate the prevalence and implication of cytochrome P450, family 2, subfamily C, polypeptide 9 (CYP2C9) variants and vitamin K epoxide reductase complex, subunit 1 (VKORC1)-1639 G > A polymorphisms in Chinese patients receiving warfarin therapy. Chinese Han patients requiring oral warfarin therapy were consecutively enrolled. Correlations between CYP2C9*1, *2, *3, *4, *5 variants and VKORC1-1639 G > A polymorphisms, fourth-day international normalized ratios (INRs) and warfarin maintenance dose were investigated. Out of 101 patients, there were no significant differences in fourth-day INR or warfarin daily maintenance doses between patients with CYP2C9*1*1 and CYP2C9*1*3 genotypes. Patients with the VKORC1-1639 AA genotype had a higher fourth-day INR (1.87 ± 0.14) than those with the VKORC1-1639 AG genotype (1.32 ± 0.15). Warfarin maintenance dose for patients with the VKORC1-1639 AA genotype (2.40 ± 0.70 mg/day) was significantly lower than for patients with the VKORC1-1639 AG genotype (4.83 ± 0.70 mg/day). Unlike Caucasian populations, VKORC1-1639 G > A polymorphisms in the Chinese population may be the dominant genetic factors associated with warfarin response variability.

Novel Oral Anticoagulants Versus Warfarin Therapy at Various Levels of Anticoagulation Control in Atrial Fibrillation—A Cost-Effectiveness Analysis

The decision as to whether to use more expensive novel oral anticoagulants (NOACs) or invest resources for quality improvement of warfarin therapy requires input from both clinical and economic analyses. Cost-effectiveness of NOACs compared to warfarin therapy at various levels of patient-time in therapeutic range (TTR) in patients with atrial fibrillation was examined, from the healthcare provider's perspective. A Markov model was used to compare life-long economic and treatment outcomes of warfarin and NOACs in a hypothetical cohort of 65-year-old atrial fibrillation patients with CHADS2 scores of 2 or above. Model inputs were derived from clinical trials published in the literature. The outcome measure was incremental cost per quality-adjusted life-year (QALY) gained (ICER). Using United States Dollar (USD) 50,000 as the threshold of willingness-to-pay per QALY, NOACs therapy was cost-effective when TTR of warfarin therapy was 60 % or below, or monthly cost of warfarin management increased by two-fold or more to achieve 70 % TTR. Warfarin therapy was cost-effective when TTR of warfarin was 70 % with up to a 1.5-fold increment in monthly cost of care, or when TTR reached 75 % with monthly cost of warfarin care increased up to three-fold. At TTR 60 %, 70 % and 75 %, NOACs was cost-effective when monthly drug cost was < USD 200, < USD 122-185 and < USD 85-145, respectively. 10,000 Monte Carlo simulations showed NOACs to be cost-effective 83.6 %, 50.7 % and 32.7 % of the time at TTR of 60 %, 70 % and 75 %, respectively. The acceptance of NOACs as cost-effective was highly dependent upon drug cost, anticoagulation control for warfarin, and anticoagulation service cost.

Imaging Diagnosis and Surgical Treatment of Popliteal Artery Entrapment Syndrome: A Single-Center Experience

In this study we report our experience with the diagnosis and surgical treatment of popliteal entrapment syndrome (PAES) over a 10-year period. Between 2002 and 2011, PAES was diagnosed in 27 limbs of 24 patients (19 males and 5 females), based on clinical symptoms and imaging examinations. The mean age of the patients was 30.4 years (range 8-69 years). All patients underwent surgical decompression of the entrapment mechanism and selective vascular reconstruction. Oral aspirin and warfarin therapy was administered after discharge. All patients underwent successful surgical treatment. No perioperative complications occurred. Clinical symptoms either disappeared or exhibited obvious improvement in all patients after surgery. No patient presented with recurrent symptoms after discharge. Doppler ultrasound during follow-up revealed the patency of the popliteal artery and saphenous vein grafts. PAES is an unusual but major cause of peripheral arterial insufficiency, particularly in patients lacking risk factors for atherosclerosis. A combination of imaging examinations is required for an early and accurate diagnosis. Surgical decompression and selective vascular reconstruction is recommended for both anatomic and symptomatic functional entrapment.

Subclavian Vein Thrombosis following Acute Internal Fixation of a Clavicular Fracture

With the recent increase in popularity of early operative fixation for certain clavicular fracture configurations, it is important for orthopaedic surgeons to be mindful of the possible additional risk of thromboembolic complications that may arise as a consequence of an acute injury. We describe the case of a 41-year-old man who presented to our department with a left-sided, middle-third, displaced clavicular fracture. He underwent an acute open reduction and internal fixation, which was complicated by a postoperative subclavian vein thrombosis. This was treated with oral anticoagulation. The thrombus had completely resorbed by 3 months. Five months after surgery, the patient had a full range of movement of the left arm, with no swelling, after having completed a 4000-mile cycle ride. A review of the available literature suggests that the commonest and safest treatment for a subclavian vein thrombosis is subcutaneous unfractionated heparin followed by oral warfarin therapy. The present case report highlights the potential risk of upper limb thrombosis after acute osteo-synthesis of the clavicle and discusses the current evidence with respect to the treatment of upper limb venous thrombosis.

Maintenance Dose of Warfarin in Sheep and Effect of Diet: A Preliminary Report

ABSTRACTSheep models are widely used to evaluate the feasibility of various cardiac assist devices. Anticoagulation therapy postoperatively, however, is seldomly reported on. Continuous heparin infusion is often used, but is cumbersome due to long-term line management with the risk of infection and dislodgement. We contemplated using warfarin instead and started a pilot dose-finding study. Three sheep were given oral warfarin between 0.1 and 0.3 mg/kg/day. Prothrombin time was monitored and INR was calculated daily. If the INR did not reach a target of 2.5–3.5, warfarin dose was doubled. We found that sheep required a dose of warfarin between 1.6 and 2.4 mg/kg/day to raise the INR to the target zone. In a subsequent study to evaluate the effect of diet on INR in sheep, three sheep were fed alfalfa hay or alfalfa pellets in a crossover design. All the animals were given warfarin at the dose of 1.6 mg/kg. The diet was switched when the INR reached the target zone of 2.5–3.5. Hay-fed animals reached the target INR on days 6 and 7. On the other hand, pellet-fed animals did not reach the target value by day 7 with the initial dose and required 2.4 mg/kg of warfarin to achieve the goal. Hay raised the INR faster and higher than pellets with the same warfarin dose. Hay may be advantageous when using oral warfarin therapy in sheep.

Placement of a retrievable inferior vena cava filter for deep venous thrombosis in term pregnancy

Venous thromboembolism is a significant cause of morbidity and death in pregnant women. Retrievable vena cava filters were placed right before labor as prophylaxis for peripartum pulmonary embolism. We reviewed the experience of caval filter placement and retrieval in term pregnancy in this study. We reviewed 15 patients with deep venous thrombosis (DVT) of the lower extremity who underwent OptEase (Cordis Corp, New Brunswick, NJ) retrievable vena cava filter placement. DVT was diagnosed by clinical symptoms and Doppler ultrasound imaging. Subcutaneous low-molecular-weight heparin was eased 12 hours before cesarean delivery and restarted 12 hours after delivery. The caval filters were placed suprarenally from the jugular approach and retrieved from the femoral approach. The filters were successfully placed in all patients on the day of cesarean delivery. No placement-related complications occurred. The caval filter was left in situ as a permanent device in one patient because the captured thrombus within the filter was not eliminated after the thrombolytic therapy. Filters in other 14 patients were retrieved successfully, without difficulty, including in one patient after complete lysis of captured thrombus by the thrombolytic therapy. Oral warfarin therapy was recommended for at least 3 months after hospital discharge, and for at least 6 months in the patient with a caval filter left in situ. All patients were examined by Doppler ultrasound imaging during the follow-up. None presented with symptomatic pulmonary embolism or filter-related complications. OptEase retrievable vena cava filter placement and retrieval in term pregnant patients with extensive DVT of the lower extremities is safe, effective, and feasible. The results in our study may justify prophylactic filter placement use right before labor.

57-Year-Old Woman With Acute Lower Extremity Pain and Swelling

A 57-year-old postmenopausal woman presented to our emergency department with a 1-day history of left leg pain, redness, and swelling. She reported no chest pain or shortness of breath. During the previous week, she made several car trips, each lasting 3 hours. Her medical history was remarkable for a left femoral and popliteal deep venous thrombosis (DVT) after breast reduction surgery during the previous year, which was treated with 1 week of subcutaneous low-molecular-weight heparin therapy and 6 months of oral warfarin therapy. She also had a history of hyperlipidemia, allergies, gastroesophageal reflux, and depression. She denied using tobacco or illicit drugs. Breast, cervical, and colon cancer screening were current and unremarkable. Daily oral medications were atorvastatin, sertraline, montelukast, and pantoprazole. She reported no family history of DVT.

Pharmacologic Reversal of Warfarin-Associated Coagulopathy in Geriatric Patients With Hip Fractures

Patients with acute hip fractures who are on maintenance warfarin for anticoagulation present a significant challenge and their management remains controversial. The purpose of this study was to assess thromboembolic and systemic complications associated with pharmacological reversal of warfarin-associated coagulopathy in a population of geriatric patients with hip fractures. This retrospective cohort study identified patients with operative hip fractures on oral warfarin therapy who had an international normalized ratio (INR) >1.50 on admission (N = 93) approximately over a 13-year span. The control group consisted of patients whose warfarin was held upon admission without further intervention preoperatively (n = 23). The treatment group consisted of patients who underwent pharmacologic reversal of elevated INR with vitamin K and/or fresh frozen plasma (FFP) in addition to holding warfarin (n = 70). Primary outcomes included thromboembolic and other complications as well as mortality within 3 months of presentation. Time to surgery was a secondary outcome. The 3-month mortality rate was 4% in the pharmacological intervention group and 17% in the watch-and-wait group; this difference trended toward statistical significance (P = .06). There were no significant differences in the likelihoods of other thromboembolic or nonthromboembolic complications between groups. While the difference in mean time to surgery was not significantly different overall between groups, this difference was significant in a subgroup of patients with higher baseline INRs (n = 46, INR >2.17), with a mean difference of 4.0 fewer days until surgery in the pharmacological intervention group (P < .01). Pharmacological reversal of warfarin-associated coagulopathy with a combination of vitamin K and FFP appears to be a safe way to optimize patients for operative fixation of hip fractures and is associated with a shorter delay to surgery in patients with more elevated INRs preoperatively. retrospective cohort study (level III).

Noninterruption of Warfarin Therapy is Safe and Does not Compromise Outcome in Patients Undergoing Endovenous Laser Therapy (EVLT)

To assess the need for cessation of oral anticoagulation with warfarin for patients undergoing endovenous laser therapy (EVLT). Between September 2004 and July 2010, 518 patients underwent 770 EVLT procedures on the lower extremity, at our institution. Of these patients, 5 underwent a total of 12 separate lower extremity EVLT procedures for the treatment of symptomatic reflux without interruption of warfarin therapy. No bleeding complications were observed during the procedure or in early follow-up. None of the patients developed a deep venous thrombosis. Complete ablation of the target vessel was observed in all patients on follow-up Duplex ultrasounds at 1 and 8 weeks postintervention. Endovenous laser therapy can be safely performed and does not compromise target vessel ablation in patients receiving oral anticoagulation warfarin therapy. Warfarin therapy should not be routinely interrupted in patients undergoing this procedure.

Ball-Shaped Thrombi in the Left Ventricular Apex

A 67-year-old man was admitted to the cardiology department because of exertional dyspnea and orthopnea aggravated for 10 days. Transthoracic echocardiography showed dilated left ventricle (LV) with global hypokinesia with severely decreased systolic function (ejection fraction was estimated to be about 15%). Two oscillating masses with smooth, spherical contour were found in the LV apex (Fig. 1A). The size of masses were estimated 22 by 29 mm and 14 by 18 mm respectively. The patient received unfractionated heparin intravenously for 5 days, followed by oral warfarin therapy. On the 8th hospital day, follow-up echocardiography revealed partial resolution of thrombi with resultant highly movable friable remnants (Fig. 1B). One the 18th hospital day, follow-up echocardiography revealed nearly complete resolution of thrombi (Fig. 1C). The patient was discharged home uneventfully. Fig. 1 Transthoracic echocardiography. Apical 4 chamber view revealed two oscillating masses with smooth, spherical contour were found in the LV apex (A). The size of masses were estimated 22 by 29 mm and 14 by 18 mm respectively. On the 8th hospital day, follow-up ... Ball shaped-masses in LV may be thrombi, vegetations or tumors. Although echocardiography is the procedure of choice for the diagnosis of cardiac mass, differentiation between myxoma and thrombus may be very difficult if the mass size is small, contours are smooth, or attachment site is atypical or ill-defined.1) Short-term anticoagulation therapy, which can differentiate thrombi from tumors, makes unnecessary surgical procedure avoidable.

Comparison of International Normalized Ratios provided by two point-of-care devices and laboratory-based venipuncture in a pharmacist-managed anticoagulation clinic

The International Normalized Ratios (INRs) measured by two point-of-care (POC) devices were compared with those obtained via laboratory-based venipuncture. In an outpatient, pharmacist-managed anticoagulation clinic, 52 patients receiving oral warfarin therapy had their INR values measured using two POC devices, i-STAT PT/INR (Abbott Laboratories, Abbott Park, IL) and CoaguChek XS Plus (Roche Diagnostics, Indianapolis, IN). At the same visit, one venous blood sample was collected from each patient for INR measurement by the reference laboratory's instrumentation (STAGO, Diagnostica-Stago, Parsippany, NJ). Accuracy was evaluated by calculating the absolute difference for each set of INR values. Clinical correlation was defined as an INR measurement obtained by the POC devices that would have resulted in the same therapeutic decision as the INR value measured by the reference laboratory's instrumentation. Accuracy was superior with the CoaguChek XS Plus device. The absolute difference (mean ± S.D.) in the INR measurements obtained using STAGO versus CoaguChek XS Plus was 0.28 ± 0.31 (p < 0.0001). The absolute difference in INR values measured using STAGO and the i-STAT PT/INR device was 0.51 ± 0.44 (p < 0.0001). For clinical correlation, 17 (33%) of 52 INR measurements with the CoaguChek XS Plus were sufficiently different from the STAGO-measured INR values to have resulted in a different therapeutic decision (p < 0.001), compared with 28 (54%) of 52 with the i-STAT PT/INR (p < 0.001). INR measurements generated by POC devices exhibited positive bias, compared with laboratory-based venipuncture, for INR values at the high end of the INR range.

Malabsorption-associated warfarin resistance

A case of malabsorption- associated warfarin resistance is reported. A 42-year-old, 111-kg, Caucasian man arrived at the emergency department with atypical pleuritic chest pain. The chest pain was associated with shortness of breath, diaphoresis, nausea, vomiting, and tachycardia. The patient's medical history was significant for multiple episodes of deep venous thrombosis (DVT) in the left upper extremity and both lower extremities, a right above-the-knee amputation due to complications of a previous DVT, insertion of a vena cava filter, pulmonary embolism (PE), asthma, hypertension, and multiple myocardial infarctions. During admission, he was diagnosed presumptively with PE. All potential causes of interference with warfarin absorption were investigated and ruled out. I.V. warfarin therapy at a conventional initial dosage of 5 mg once daily was started on hospital day 2. The International Normalized Ratio (INR) reached the therapeutic range after increasing the i.v. warfarin dosage to 7.5 mg once daily on hospital day 6. The ability to obtain a therapeutic INR on a relatively low dosage of i.v. warfarin but not high dosages of oral warfarin strongly suggests an inherent warfarin malabsorption defect in this patient. A 42-year-old man with a history of recurrent thromboembolisms demonstrated resistance to oral warfarin therapy due to warfarin malabsorption.

Clinical Utility and Accuracy of Coaguchek® XS, a Reliable Alternative to Laboratory International Normalized Ratio Monitoring in Korean Patients With Atrial Fibrillation

Background and Objectives: To evaluate the accuracy and the clinical utility of the Coaguchek ® XS, a portable point-of-care coagulometer, compared to standard laboratory methods in Korean patients. Subjects and Methods: We included 107 patients with atrial fibrillation on long-term oral warfarin therapy. The prothrombin time as expressed by the international normalized ratio (INR) was measured by the portable Coaguchek ® XS system as well as standard laboratory methods. Agreement between the two methods was defined as a difference of less than 0.3 between the INR values. Results: The INR determined by the portable Coaguchek ® XS had excellent correlation with the values obtained by standard methods (r=0.984, p 3.0). There was a 91.6% agreement between the two methods. Only nine cases (8.4%) had a difference of more than 0.3; this was mainly noted in the high INR group. Conclusion: The portable self-testing of the INR by the Coaguchek ® XS might be a reliable