Role of Electrode Configuration and Morphology in Printed Prothrombin Time Sensors

Patients on long-term anticoagulation therapy require frequent testing of prothrombin time/international normalized ratio (PT/INR) to ensure therapeutic efficacy. Point-of-care (POC) PT tests for at-home monitoring eliminate the burden of visiting the clinic, but realizing a cost-effective and robust at-home POC test for PT has remained elusive. Recent demonstrations of printed PT sensors show promise for addressing the cost concerns; however, the printed sensors have lacked quality control to ensure reliability between tests. In this work, on-chip redundancy is introduced with fully printed impedimetric PT sensors by incorporating simultaneous testing with a single fingerstick volume of blood (8 μL). The influence of electrode dimensions and composition were studied, revealing an optimal electrode spacing of 200 μm and an unexpected dependence on the morphology of the electrodes. Three distinct silver morphologies were studied: aerosol jet printed silver nanoparticles (AgNPs), aerosol jet printed silver nanowires (AgNWs), and evaporated silver (Ag). In general, AgNPs exhibited the best PT sensor performance, due to relatively low conductance and high porosity. Overall, the printed impedimetric PT sensor functionalization was improved by incorporating simultaneous testing and, when combined with a handheld control device, shows promise for leading to a system that overcomes the challenges of commercial PT/INR coagulometers.

Serum uric acid level in chronic liver disease and its correlation with Child-Pugh score in a tertiary care hospital from South India

Background

Chronic liver disease (CLD) is one of the important causes of morbidity and mortality in our country, and since the damage to the liver is irreversible, we have to look for many severity markers or predictors for the prognosis of the patient. In this study, we have tried to correlate the level of serum uric acid (UA) with the severity of CLD presented as a Child-Pugh score.

Methods

A cross-sectional observational study was conducted at Vijayanagar Institute of Medical Science (VIMS), Ballari, Karnataka, from October 2015 to June 2017 in the Department of General Medicine. Fifty patients diagnosed with CLD, aged between 18 and 65 years, of either gender, were enrolled in the study. Serum UA levels were measured, and liver function and coagulation parameters were assessed. A statistical analysis was performed to evaluate the association between serum UA levels, liver function test, and coagulation parameters.

Results

In our study, the mean serum UA level was 6.52 mg/dl and was raised in patients with CLD in correlation to its severity. Alcoholic liver disease (ALD) was the most common etiology for CLD (80%) followed by hepatitis B (Hep B) virus infection (12%) and hepatitis C (Hep C) virus infection (6%). Serum UA levels increased as the Child-Turcotte-Pugh (CTP) score increased. The mean UA level in CTP class C was 8.29 mg/dl. Various parameters such as serum aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase, total bilirubin, international normalized ratio (INR), calcium, and albumin were significantly associated with serum UA levels in CLD patients.

Conclusion

The correlation between rising blood UA levels and the Child-Pugh score shows that UA estimate may be a valid and affordable indicator for assessing the extent of liver cirrhosis in CLD.

Elevated INR in a COVID-19 patient after concomitant administration of azvudine and anticoagulants

Background: Azvudine (FNC) is a promising treatment candidate for managing coronavirus disease 2019 (COVID-19). However, drug interactions with azvudine have been poorly studied, especially with no reported cases of azvudine with anticoagulants such as warfarin and rivaroxaban. Case summary: The patient was diagnosed with lower limb venous thrombosis and took warfarin regularly. The international normalized ratio (INR) was stable (2.0-3.0). However, the INR increased to 7.52 after administering azvudine. The patient had no other factors justifying this change. This increase in INR occurred again with the administration of azvudine in combination with rivaroxaban, and the INR increased to 18.91. After azvudine administration was stopped, the INR did not increase when rivaroxaban was used alone. Conclusion: Azvudine, warfarin, and rivaroxaban might have previously unidentified drug interactions that increased the INR. Therefore, the INR must be closely monitored when they are concomitantly administered in COVID-19 patients.

Reversal of Oral Vitamin K Antagonists Using Prothrombin Complex Concentration Prior to IV tPA Administration

Herein, we report two acute ischemic stroke cases that we used prothrombin complex to reverse the effects of warfarin in order to apply intravenous thrombolytic treatment. To the best of our knowledge, there are only limited amount of cases that prothrombin complex concentrates were applied prior to intravenous thrombolytic treatment administration. As one of the biggest acute stroke clinics in our country, we aim to open a discussion for this treatment to be fully researched and understood.

Increased INR Values Predict Accelerating Deterioration and High Short-Term Mortality Among Patients Hospitalized With Cirrhosis or Advanced Fibrosis

Background and Objective: An increase in the international normalized ratio (INR) is associated with increased mortality in patients with cirrhosis and other chronic liver diseases, while little is known about the quantitative relationship. This study aimed to investigate the quantitative relationship between the INR and short-term prognosis among patients hospitalized with cirrhosis or advanced fibrosis and to evaluate the role of the INR as a risk factor for short-term liver transplant (LT)-free mortality in these patients.

Patients and Methods: This study prospectively analyzed multicenter cohorts established by the Chinese Acute-on-Chronic Liver Failure (CATCH-LIFE) study. Cox regression was used to describe the relationship between the INR and independent risk factors for short-term LT-free mortality. Forest plots were used in the subgroup analysis. Generalized additive models (GAMs) and splines were used to illustrate the quantitative curve relationship between the INR and the outcome and inflection point on the curve.

Results: A total of 2,567 patients with cirrhosis and 924 patients with advanced fibrosis were included in the study. The 90-day LT-free mortality of patients with cirrhosis and advanced fibrosis was 16.7% (428/2,567) and 7.5% (69/924), respectively. In the multivariable Cox regression analysis, the increase in the INR was independently associated with the risk of 90-day LT-free mortality both in patients with cirrhosis (HR, 1.06; 95% CI, 1.04–1.07, p < 0.001) and in patients with advanced fibrosis (HR, 1.09; 95% CI, 1.06–1.12, p < 0.001). An INR of 1.6/1.7 was found to be the starting point of coagulation dysfunction with a rapid increase in mortality in patients with cirrhosis or in patients with advanced fibrosis, respectively. A 28-day LT-free mortality of 15% was associated with an INR value of 2.1 in both cirrhosis and advanced fibrosis patients.

Conclusions: This study was the first to quantitatively describe the relationship between the INR and short-term LT-free mortality in patients with cirrhosis or advanced fibrosis. The starting points of INR indicating the rapid increase in mortality and the unified cutoff value of coagulation failure in cirrhosis and advanced fibrosis, will help clinicians accurately recognize early disease deterioration.

Tele-pharmacy Anticoagulation Clinic During COVID-19 Pandemic: Patient Outcomes

Introduction: It is well-established that clinical pharmacist-managed anticoagulation services achieve superior anticoagulation control, with a positive impact. At King Abdulaziz Medical City (KAMC), Riyadh, Saudi Arabia, the structure of anticoagulation management is a pharmacist-managed specialty service. With the current COVID-19 situation, measures were taken to assure the continuity of patient care by establishing tele-pharmacy anticoagulation clinics. Materials and Methods: This was a prospective study with patients prescribed anticoagulation and followed up for 3 months. Since establishing the anticoagulation virtual clinic in March 2020, 270 patients were recruited in the study. The data collected included age, gender, comorbidities, indication for anticoagulation, intended duration of treatment, warfarin dose, testing of International Normalized Ratio (INR), INR target, range of INR values, time INR that was within the therapeutic range (TTR), and complications of therapy (bleeding and/or bruises). The patients were asked to complete the pharmacist satisfaction survey (PSS) after their consultation to assess patient satisfaction with the new virtual consultation system. Linguistic and cultural validation was conducted for the questionnaire. Results: A total of 270 patients were included in the study. The mean percentage of overall INR values in the range was 59.39% ± 32.84, and the mean time with the overall INR was within the therapeutic range 57.81% ± 32.08. Thirty-one percent of the sample had good anticoagulation control (time in therapeutic range >70%). The median satisfaction score was 32 (IQR 28-36) with a maximum score of 40. Conclusion: This is the first study to assess the tele-pharmacy anticoagulation clinic's efficiency and patient satisfaction in Saudi Arabia during the COVID-19 pandemic. This type of consultation was as effective as face-to-face consultations. The study also highlighted that though the reduction in the cost of care was not substantial, there was a significant increase in resource (clinical pharmacist) utilization as a result of this model. The adoption of tele-pharmacy resulted in time savings for the clinical pharmacists who can be utilized in many other improvement projects in adult ambulatory clinics to ensure the delivery of better quality and safe patient care.

Elevated INR in a COVID-19 patient after concomitant administration of favipiravir and warfarin: A case report

What is known and objective

Favipiravir is a promising treatment candidate for managing coronavirus disease 2019 (COVID‐19). Warfarin has many drug interactions, but no interactions with favipiravir have been reported.

Case summary

Our patient was taking warfarin for deep vein thrombosis. The international normalized ratio (INR) was stable (1.65 to 2.0); however, it increased to 4.63 after administering favipiravir. The patient had no other factors justifying this change.

What is new and conclusion

Favipiravir and warfarin might have previously unidentified drug interactions that elevated the INR. Therefore, INR must be closely monitored when they are concomitantly administered in COVID‐19 patients.

Evolving Paradigm of Prothrombin Time Diagnostics with Its Growing Clinical Relevance towards Cardio-Compromised and COVID-19 Affected Population

Prothrombin time (PT) is a significant coagulation (hemostasis) biomarker used to diagnose several thromboembolic and hemorrhagic complications based on its direct correlation with the physiological blood clotting time. Among the entire set of PT dependents, candidates with cardiovascular ailments are the major set of the population requiring lifelong anticoagulation therapy and supervised PT administration. Additionally, the increasing incidence of COVID affected by complications in coagulation dynamics has been strikingly evident. Prolonged PT along with sepsis-induced coagulopathy (SIC score > 3) has been found to be very common in critical COVID or CAC-affected cases. Considering the growing significance of an efficient point-of-care PT assaying platform to counter the increasing fatalities associated with cardio-compromised and coagulation aberrations propping up from CAC cases, the following review discusses the evolution of lab-based PT to point of care (PoC) PT assays. Recent advances in the field of PoC PT devices utilizing optics, acoustics, and mechanical and electrochemical methods in microsensors to detect blood coagulation are further elaborated. Thus, the following review holistically aims to motivate the future PT assay designers/researchers by detailing the relevance of PT and associated protocols for cardio compromised and COVID affected along with the intricacies of previously engineered PoC PT diagnostics.

Warfarin Dose Requirements in Adults Hospitalized With COVID-19 Infection: A Retrospective Case Series

PURPOSE

To describe the impact of hospitalization with COVID-19 infection on warfarin dose requirements in adult inpatients.

SUMMARY

A retrospective chart review of 8 adults on warfarin admitted to Michigan Medicine with COVID-19 infection was conducted and reported as a case series. Outcomes of interest were difference in average daily dose of warfarin prior to admission (PTA) and while inpatient (IP), warfarin sensitivity, time in therapeutic range (TTR), confirmed or suspected thromboembolic event, any major or clinically significant bleeding episodes, and in-hospital mortality. IP average daily warfarin doses were lower when compared to PTA average daily doses [1.3 mg (1.3) vs. 6.2 mg (4.1)]. The mean percentage decrease in dose was 68.8% (23) and the mean absolute dose difference was 4.8 mg (4.3). Mean IP percentage tests in range was 30.8% (24.6) and mean IP warfarin sensitivity was 4.2 (3.8), both of which differed from PTA TTR and warfarin sensitivity for those with data available (n = 3, n = 6, respectively). One patient was treated for suspected acute pulmonary embolism while on warfarin and one patient experienced clinically relevant bleeding. In-hospital mortality was zero, mean length of stay (LOS) was 17 days (14.4), and mean intensive care unit (ICU) LOS for the 3 patients requiring ICU level care was 14.3 days (4.5).

CONCLUSION

Decreased warfarin dose requirements were evident in this group of adults hospitalized with COVID-19 infection. These findings suggest lower doses of warfarin may be needed to achieve therapeutic anticoagulation while inpatient.

Nonalcoholic fatty liver disease impacts the control of the international normalized ratio in patients with atrial fibrillation

Background

It is unclear whether the therapeutic effect of warfarin in patients with atrial fibrillation (AF) and normal liver function differs between those with and without nonalcoholic fatty liver disease (NAFLD). With this in mind, we aimed to evaluate the impact of NAFLD on the international normalized ratio (INR) control in warfarin-treated AF patients with normal liver function.

Methods

We enrolled 600 AF patients aged 28–94 (median 68) with normal liver function who were receiving daily warfarin therapy, 172 with NAFLD and 428 without. The INR and INR/warfarin dosage rate were measured. Four nested multivariable linear regression models adjusted for potential confounders were used to assess whether there were differences in INR and INR/warfarin dose rate between patients with and without NAFLD.

Results

The INR, the percentage of patients with INR within the target range of 2.0–3.0, and the INR/warfarin dose rate were lower in patients with NAFLD than those without. In the maximally adjusted multivariable linear regression models, the INR in NAFLD patients (0.22±0.07, P=0.003) was lower than in non-NAFLD patients, and the INR/warfarin dose rate was slightly lower (0.09±0.06, P=0.10) in NAFLD than in non-NAFLD patients.

Conclusions

Our findings suggest that among AF patients, the therapeutic effect of warfarin is impaired in patients who have NAFLD. Therefore, a slightly higher or personally optimized dosage of warfarin might be necessary among AF patients with NAFLD in order to achieve the INR target range.

Relationship between initial international normalized ratio and prognosis in patients with cardiogenic cerebral embolism

BACKGROUND

Cardiogenic cerebral embolism is one of the most common causes of ischemic stroke. In general, cardioembolic stroke is associated with more severe neurological deficits and higher early mortality, as well as a worse functional outcome. Oral anticoagulant (OAC) therapy could reduce the risk of stroke significantly. However, several limitations have led to it being underused, which raises the failure of anticoagulant therapy. This study aimed to investigate the patients with atrial fibrillation presented cardioembolic stroke who underwent OAC therapy, and to assess treatment efficacy, and outcomes, especially the international normalized ratio (INR) value in the acute phase.

METHODS

Clinical data of 306 patients with cardioembolic stroke and etiology of atrial fibrillation were retrospectively analyzed, and demographics, cardiovascular risk factors, embolic cardiopathy, CHADS2 and CHA2DS2-VASc score, HAS-BLED score, INR value, TOAST subtypes, OCSP classification, modified Rankin Scale (mRS) scores and prognosis were evaluated.

RESULTS

The median score on the CHADS2 and CHA2DS2-VASc scales was 3 and 4, respectively; The median score on the HAS-BLED scale was 2. Only 33 patients (10.8%) were in therapeutic INR range at the onset of stroke. In the acute phase, 233 patients (76.1%) continued to use OAC therapy, and 73 patients were suspended. Eighteen patients (24.7%) resumed treatment after an average of 32 days. Thirty-nine of 251 survivors with nonvalvular atrial fibrillation were modified to novel oral anticoagulants (NOACs). At 3 months follow-up, patients with INR ≥1.7 had significantly better prognosis than those with INR <1.7, both in the percentage of patients with functional independence (78.9% vs. 41.2%) and in mortality (7.0% vs. 25.0%) (P<0.001).

CONCLUSIONS

Patients presented cardioembolic stroke despite being treated with OAC, especially those with a subtherapeutic INR value, raises the failure of anticoagulant therapy. Despite the ineffectiveness of the OAC, the prognosis is better when the INR ≥1.7 at the initiation of the stroke.

[Argentine Consensus in effective management of anticoagulation clinics for the use of vitamin k antagonists]

Treating an anticoagulated patient with vitamin K antagonists (VKA) remains a challenge, especially in areas where dicoumarins are still the first drug of choice due to the cost of other oral anticoagulants. Anticoagulation clinics have proven to be the most efficient and safe way to avoid thrombotic and hemorrhagic complications and to keep patients in optimal treatment range. However, they require adequate infrastructure and trained personnel to work properly. In this Argentine consensus we propose a series of guidelines for the effective management of the anticoagulation clinics. The goal is to achieve the excellence in both the clinical healthcare and the hemostasis laboratory for the anticoagulated patient. The criteria developed in the document were agreed upon by a large group of expert specialists in hematology and biochemistry from all over the country. The criteria presented here must always be considered when indicating VKA although they had to be adapted to the unequal reality of each center. Taking these premises into consideration will allow us to optimize the management of the anticoagulated patient with VKA and thus minimize thrombotic and hemorrhagic intercurrences, in order to honor our promise not to harm the patient.

Warfarin-Induced Rapid Rise in INR Post-Cardiac Surgery Is Not Associated With Increased Bleeding Risk

Background: Post-cardiac surgery bleeding can have devastating consequences, and it is unknown if warfarin-induced rapid international normalized ratio (INR) rise during the immediate postoperative period increases bleed risk. Objective: To determine the impact of warfarin-induced rapid-rise INR on post-cardiac surgery bleeding. Methods: This was a single-center, retrospective chart review of post-cardiac surgery patients initiated on warfarin at Mayo Clinic Hospital, Rochester. Patients were grouped based on occurrence or absence of rapid-rise INR (increase ≥1.0 within 24 hours). The primary outcome compared bleed events between groups. Secondary outcomes assessed hospital length of stay (LOS) and identified risk factors associated with bleed events and rapid rise in INR. Results: During the study period, 2342 patients were included, and 56 bleed events were evaluated. Bleed events were similar between rapid-rise (n = 752) and non-rapid-rise (n = 1590) groups in both univariate (hazard ratio [HR] = 1.22; P = 0.594) and multivariable models (HR = 1.24; P = 0.561). Those with rapid-rise INR had longer LOS after warfarin administration (discharge HR = 0.84; P = 0.0002). The most common warfarin dose immediately prior to rapid rise was 5 mg. Risk factors for rapid-rise INR were low body mass index, female gender, and cross-clamp time. Conclusion and Relevance: This represents the first report to assess warfarin-related rapid-rise INR in post-cardiac surgery patients and found correlation to hospital LOS but not bleed events. Conservative warfarin dosing may be warranted until further research can be conducted.

International normalized ratio (INR) testing in Europe: between-laboratory comparability of test results obtained by Quick and Owren reagents

Background:

This study was designed to obtain an overview of the analytical quality of the prothrombin time, reported as international normalized ratio (INR) and to assess the variation of INR results between European laboratories, the difference between Quick-type and Owren-type methods and the effect of using local INR calibration or not. In addition, we assessed the variation in INR results obtained for a single donation in comparison with a pool of several plasmas.

Methods:

A set of four different lyophilized plasma samples were distributed via national EQA organizations to participating laboratories for INR measurement.

Results:

Between-laboratory variation was lower in the Owren group than in the Quick group (on average: 6.7% vs. 8.1%, respectively). Differences in the mean INR value between the Owren and Quick group were relatively small (<0.20 INR). Between-laboratory variation was lower after local INR calibration (CV: 6.7% vs. 8.6%). For laboratories performing local calibration, the between-laboratory variation was quite similar for the Owren and Quick group (on average: 6.5% and 6.7%, respectively). Clinically significant differences in INR results (difference in INR>0.5) were observed between different reagents. No systematic significant differences in the between-laboratory variation for a single-plasma sample and a pooled plasma sample were observed.

Conclusions:

The comparability for laboratories using local calibration of their thromboplastin reagent is better than for laboratories not performing local calibration. Implementing local calibration is strongly recommended for the measurement of INR.

Clinical effect of enoxaparin on international normalized ratio following hepato-pancreatico-biliary and gastroesophageal resection

BACKGROUND AND OBJECTIVES

Enoxaparin inactivates factor Xa via a complex formed after binding to circulating anti-thrombin III. This mechanism is reported not to alter hemostatic measures such as clotting time, PT, or PTT. To date, no clinical trials have shown a causal relationship between the clinical/pharmacological effects of enoxaparin on international normalized ratio (INR). The aim of our study is to show the clinical effect of enoxaparin on INR.

METHODS

Patients (N = 350) were reviewed from our prospective IRB approved databases undergoing gastroesophageal or hepatobiliary surgeries. INR levels were recorded for 6 days: pre-operative to 5 days after surgery.

RESULTS

Patients (N = 289) received enoxaparin daily starting post-operative day 1, while 61 patients who did not receive enoxaparin were used as controls. The mean post-operative INR in both the 30 and 40 mg groups were both significantly higher than the mean post-operative INR of the control group (P = 0.015 and P = 0.00075, respectively); however postoperative hemoglobin levels were not significantly lower in the enoxaparin versus control.

CONCLUSION

This is the first clinical evidence of the effect of enoxaparin on INR in patients undergoing abdominal surgeries for malignancies. We demonstrate an increase in the INR for patients who received enoxaparin for post-operative VTE prophylaxis.

[Randomized Comparison of Two Approaches to Initial Warfarin Dosing: Time in Therapeutic Range of International Normalized Ratio During Hospitalization]

AIM

To perform a randomized, open-label comparison of average time in therapeutic range (TTR) of international normalized ratio (INR) using two approaches to initial warfarin dosing during hospitalization: the standard method and the one using individual patient characteristics (clinical algorithm - the studied approach).

MATERIALS AND METHODS

We randomly assigned 60 patients with different indications for vitamin K antagonist therapy to the studied approach (n=31, intervention group) or to the standard method (n=29, control group). А target INR range for all patients was 2.0 to 3.0.

RESULTS

The average TTR and portions of INR values within target range during the whole time of drug dosing turned out to be small. TTR was 22.4% with standard method and 21.4% with clinical algorithm, which was well below desired 60%.

CONCLUSION

The opportunities for achieving target INR in inpatient settings, regardless of warfarin dosing regimen, are limited.

Advantages of a Warfarin Protocol for Long-term Care Pharmacists: a Retrospective Cohort Study

Background

Warfarin is an anticoagulant prescribed to 12% of long-term care residents to reduce the risk of thrombo-embolism. This study used indicators to compare warfarin management by pharmacists to usual care.

Methods

This was a retrospective cohort study comparing a pharmacist-managed warfarin protocol with usual care of qualified warfarin recipients at long-term care facilities (two protocol, one control) in Calgary, Alberta. We compared the proportion of international normalized ratio (INR) tests in the range 2.0 to 3.0, time in range, number of tests, and frequency of bleeding at protocol and control sites. Our primary outcome, time in INR therapeutic range, is an indicator for assuring care quality. A cross-sectional survey at these sites compared health professionals’ perceptions of workload and effectiveness of warfarin management.

Results

Of the 197 residents’ charts reviewed in the study period, those on protocol had 45.0 INR tests while those on usual care had 52.7 tests (p = .034, 95% CI for the difference: 0.6 to 14.6 INR tests). No significant difference was found for time in therapeutic range, number of tests in range, or major bleeding events. Of 178 health professionals surveyed, those from protocol facilities were more satisfied with warfarin management (p = .013). Workload and safety were perceived similarly at all sites.

Interpretation

Our results suggest that a pharmacist-managed warfarin protocol is as effective as usual care and has advantages pertaining to work satisfaction, knowledge of drug interactions, consistent documentation, and fewer INR tests. Further research on teamwork and coagulation management in long-term care facilities is recommended.

Association of gene polymorphisms with the risk of warfarin bleeding complications at therapeutic INR in patients with mechanical cardiac valves

WHAT IS KNOWN AND OBJECTIVE

Pharmacogenetic studies of the genetic regulation of warfarin dose requirement have been reported, but few have been on the bleeding complications at therapeutic international normalized ratio (INR). This study aimed to evaluate the effect of gene polymorphisms of CYP2C9, VKORC1, thrombomodulin (THBD) and C-reactive protein (CRP) on the risk of bleeding complications of warfarin at therapeutic INR in Korean patients with mechanical cardiac valves.

METHODS

A retrospective warfarin pharmacogenetic association study was performed. One hundred and forty-two patients with mechanical cardiac valves who were on warfarin anticoagulation therapy and maintained INR levels of 2·0-3·0 for 3 consecutive time intervals were followed up. CYP2C9 rs1057910, VKORC1 rs9934438, CRP rs1205, THBD rs1042580 and THBD rs3176123 were genotyped. The association between genotypes and warfarin bleeding complications was evaluated using logistic regression analysis, adjusted for demographic and clinical factors.

RESULTS AND DISCUSSION

Of 142 eligible patients, 21 patients (14·8%) had bleeding complications at therapeutic INR. Patients with the G allele in THBD rs1042580 (AG or GG) had a lower risk of bleeding than patients with the AA genotype (adjusted OR: 0·210, 95% CI: 0·050-0·875, P = 0·032). The THBD rs3176123 polymorphism did not show any association with bleeding. For CRP rs1205, patients with the A allele (GA or AA genotype) had a higher risk of bleeding than patients with the GG genotype (adjusted OR: 5·575, 95% CI: 1·409-22·058, P = 0·014). Variant VKORC1 and CYP2C9 genotypes did not confer a significant increase in the risk for bleeding complications.

WHAT IS NEW AND CONCLUSIONS

As expected, no association could be found between bleeding complications and two dose-related genes (CYP2C9*3 and VKORC1 rs9934438). In contrast, our results suggest that two genetic markers (THBD rs1042580 and CRP rs1205) could be predictors of bleeding complications of warfarin at normal INR. Given the retrospective study design and the relatively small sample size, our hypothesis requires further independent validation using more robust prospective designs. However, additional retrospective studies similar to ours but in populations with different genetic backgrounds should also be useful.

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

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSIONS

Unlike Caucasian populations, VKORC1-1639 G > A polymorphisms in the Chinese population may be the dominant genetic factors associated with warfarin response variability.