Evaluating the impact of study-level factors on warfarin control in U.S.-based primary studies: a meta-analysis

Low Quality of Warfarin Therapy is Associated With Female Gender but Not With Polypharmacy in Patients With Atrial Fibrillation

Background: We examined the impact of polypharmacy on the quality of the anticoagulation therapy in patients with atrial fibrillation. We also examined the factors that affect the stability of warfarin therapy.

Methods and Results: This retrospective study was conducted using data from 157 consecutive outpatients with atrial fibrillation in a single tertiary referral hospital. Patients who were prescribed warfarin continuously and for whom PT-INR was examined at least three times in a year were included in this study. We examined the quality of warfarin therapy using time in the therapeutic INR range (TTR), percentage of PT-INR determinations in range (PINRR), and the coefficient variation (CV) of PT-INR. We found that the number of prescribed medicines was significantly associated with high BMI and low eGFR, but not with TTR, PINRR, and the coefficient variation of PT-INR in patients with atrial fibrillation. We also found that female gender was independently associated with low PINRR in this study population.

Conclusion: Polypharmacy did not deteriorate the quality of warfarin therapy in patients with atrial fibrillation treated in the tertiary referral hospital. Female gender was an independent predictor of the low quality of warfarin therapy.

Individual and monitoring centre influences upon anticoagulation control of AF patients on warfarin: A longitudinal multi-centre UK-based study

OBJECTIVES

Time within therapeutic INR range (TTR) predicts benefits/risk of warfarin therapy. Identification of individual- and centre-related factors that influence TTR, and addressing them to improve anticoagulation control, are important. This study examined the impact of individual and centre-related factors upon long-term anticoagulation control in atrial fibrillation patients in seven UK-based monitoring services.

METHODS

Data between 2000 and 2014 on 25 270 patients (equating to 203 220 patient years) [18 120 (71.7%) in general practice, 2348 (9.3%) in hospital-based clinics and 4802 (19.0%) in domiciliary service] were analysed.

RESULTS

TTR increased with increasing age, peaking around 77% at 70-75 years, and then declined, was lower in females than males, and in dependent home-monitored patients than those attending clinic (P < 0.0001). TTR, number of dose changes and INR monitoring events and the probability of TTR ≤ 65%, differed across the centres (P < 0.0001).

CONCLUSIONS

Although all the participating centres ostensively followed a standard dosing algorithm, our results indicate that variations in practice do occur between different monitoring sites. We suggest feedback on TTR for individual monitoring sites gauged against the average values reported by others would empower the individual centres to improve quality outcomes of anticoagulation therapy by identifying and adjusting contributory factors within their management system.

Postthrombotic Syndrome in Patients Treated With Rivaroxaban or Warfarin for Venous Thromboembolism

Postthrombotic syndrome (PTS) is a frequent complication of venous thromboembolism (VTE). Using MarketScan claims data from January 2012 to June 2015, we identified adults with a primary diagnosis code for VTE during a hospitalization/emergency department visit, ≥6 months of insurance coverage prior to the index event and newly started on rivaroxaban or warfarin within 30 days of the index VTE. Patients with <4-month follow-up postindex event or a claim for any anticoagulant during 6-month baseline period were excluded. Differences in baseline characteristics between rivaroxaban and warfarin users were adjusted for using inverse probability of treatment weights based on propensity scores. Patients were followed for the development of PTS starting 3 months after the index VTE. Cox regression was performed and reported as hazard ratios with 95% confidence intervals (CIs). In total, 10 463 rivaroxaban and 26 494 warfarin users were followed for a mean of 16 ± 9 (range, 4-39) months. Duration of anticoagulation was similar between cohorts (median = 6 months). Rivaroxaban was associated with a 23% (95% CI: 16-30) reduced hazard of PTS versus warfarin. Rivaroxaban was associated with a significant risk reduction in symptoms of PTS compared to warfarin in patients with VTE treated in routine practice.

Comparison of Warfarin use in terms of efficacy and safety in two different polyclinics

Objective:

This study compared the efficacy and safety of warfarin in specialized international normalized ratio (INR) outpatient clinic (INR-C) and in general cardiology outpatient clinic (General-C).

Methods:

Herein, 381 consecutive patients with a regular follow-up at INR-C (n=233) or General-C (n=148) for at least 1 year were retrospectively included. While INR-C patients were followed by a single experienced trained nurse, General-C patients were followed by a different cardiologist who worked in a rotational principle every month. During controls, demographic characteristics, INR levels, bleeding events, ischemic stroke, and transient ischemic attacks in the last 1 year were recorded. Primary endpoint was defined as the evaluation of the combined major bleeding and ischemic event, and secondary endpoint was defined as the evaluation of them separately.

Results:

The mean age of the patients was 62±12.86 and 43.8% were male. Mean time in therapeutic range (TTR) level was statistically higher in INR-C than that in General-C (68.8%±15.88 and 51.6%±23.04, respectively; p<0.001). Primary outcomes were significantly higher in General-C than that in INR-C [13.5% (20) and 6.4% (15); respectively, p=0.020]. Overall, major bleeding was observed in 25 patients (6.5%) and (2.6%) ischemic event was observed in 10 patients. In General-C patients, both major bleeding (8.8% vs. 5.2%; p=0.163) and the ischemic event (4.7% vs. 1.3%; p=0.051) were more, and no statistically significant differences were detected between the two clinics.

Conclusion:

The findings of our study demonstrate that patients followed in INR-C had higher TTR levels and lower bleeding and ischemic events rates that those followed in General-C.

INR Stability, Clinical Importance, and Predictors in Patients With Atrial Fibrillation and Venous Thromboembolism Receiving Vitamin K Antagonists

Objective: Compare and contrast systematic reviews/meta-analyses assessing the time in the therapeutic range (TTR) for vitamin K antagonists (VKAs), clinical impact, and predictors. Data Sources: OVID MEDLINE search (1980-June 1, 2016) using the terms “vitamin K antagonist or warfarin” and “systematic review or meta-analysis” with backwards citation tracking from procured articles. Study Selection and Data Extraction: Search results were limited to systematic reviews assessing TTR with VKAs in patients with atrial fibrillation (AF) or venous thromboembolism (VTE). Data Synthesis: Six systematic reviews assessed TTR (4 in AF, 2 in VTE), and 3 of those assessed control at the time of a thrombotic or bleeding event (2 in AF, 1 in VTE). In patients on VKAs, greater TTR is correlated with fewer thromboembolic events and bleeding complications. VKA naïve patients have a harder time maintaining TTR than those with a previous knowledge of the likely therapeutic dose. Patients in the United States spend less TTR than those in other countries. Randomized clinical trials and anticoagulation clinics achieve greater TTR than those treated outside of these settings. The overall TTR has not improved from the first systematic reviews to the newest ones even though they were conducted 10 years apart and contained many new studies. Also, TTR in AF and VTE is similar. Conclusions: TTR is an important metric of VKA efficacy and safety and needs to be optimized. Many factors such as being VKA naïve can compromise TTR, and the use of anticoagulation clinics to optimize therapy is an important approach.

Vitamin K antagonist use: evidence of the difficulty of achieving and maintaining target INR range and subsequent consequences

Vitamin K antagonists (VKAs) are effective oral anticoagulants that are titrated to a narrow therapeutic international normalized ratio (INR) range. We reviewed published literature assessing the impact of INR stability - getting into and staying in target INR range - on outcomes including thrombotic events, major bleeding, and treatment costs, as well as key factors that impact INR stability.

A time in therapeutic range (TTR) of ≥65 % is commonly accepted as the definition of INR stability. In the real-world setting, this is seldom achieved with standard-of-care management, thus increasing the patients’ risks of thrombotic or major bleeding events. There are many factors associated with poor INR control. Being treated in community settings, newly initiated on a VKA, younger in age, or nonadherent to therapy, as well as having polymorphisms of CYP2C9 or VKORC1, or multiple physical or mental co-morbid disease states have been associated with lower TTR. Clinical prediction tools are available, though they can only explain <10 % of the variance behind poor INR control.

Clinicians caring for patients who require anticoagulation are encouraged to intensify diligence in INR management when using VKAs and to consider appropriate use of newer anticoagulants as a therapeutic option.

Anticoagulation Control in Swiss Primary Care: Time in Therapeutic Range Percentages Exceed Benchmarks of Phase III Trials

BACKGROUND

In randomized controlled trials, non-vitamin K antagonist oral anticoagulants (NOACs) demonstrated noninferiority to vitamin K antagonists (VKAs) in patients who spent limited time in therapeutic range (TTR). In real-life patients, TTR is known to vary significantly across countries and health-care settings.

OBJECTIVE

We aim to evaluate the quality of VKA treatment in Swiss primary care (PC) by comparing patients' median TTR to levels achieved in the phase III NOAC trials RE-LY, ROCKET-AF, ARISTOTLE, and ENGAGE-AF-TIMI 48. Patient characteristics affecting TTR control shall be estimated.

METHODS

This is a retrospective longitudinal study in Swiss PC patients receiving VKA for ≥6 months. We identified patients from the PC research database FIRE (Family medicine International Classification of Primary Care Research using Electronic medical records) and calculated TTR according to Rosendaal formula. Comparative data from NOAC trials were retrieved from medical literature. Linear regression models were used to assess predictors of TTR.

RESULTS

Primary care encounters of 215 patients were analyzed. Like in the NOAC trials, median observation period was 2.2 years, but patients were older (67.9% vs 38% ≥75 years) and differed in terms of concomitant diseases and drugs. Median TTR was 75% (65% in the NOAC trials). Female sex was independently associated with a lower TTR and significantly modified by increasing age.

CONCLUSION

Practitioners should consider that patients in NOAC trials are only partly representative of PC patients, particularly in terms of TTR control. Only a minority of the observed patients would require a therapy switch to NOACs due to inadequate TTR. Further research is needed in order to identify specific features of care management that are associated with these outcomes.

Center-Related Determinants of VKA Anticoagulation Quality: A Prospective, Multicenter Evaluation

Background

Center-specific TTR (c-TTR) is a measure reporting the mean patient TTR within an anticoagulation clinic describing the quality of anticoagulant monitoring offered by that clinic. c-TTR has a considerable between-center variation, but its determinants are poorly understood.

Objectives

We aimed at evaluating which clinical, procedural or laboratory factors could be associated with c-TTR variability in a multicenter, observational cross-sectional study over a five-year period.

Patients/Methods

Data from 832,204 individual patients followed for VKA therapy in 292 Centers affiliated with the Italian Federation of Anticoagulation Clinics (FCSA) were analyzed. c-TTR was computed based on the TTR of patients followed at each Center, and a mixed linear regression model was used for a predefined set of explanatory variables.

Results

The Center next-visit interval ratio (the mean number of days after a visit with an INR outside the therapeutic range, divided by the days after a visit with an INR within the therapeutic range), the Center mean patient INR and the Center laboratory performance at EQA proficiency testing were the only variables that were independently associated with c-TTR (β-coefficients -17.32, 9.67, and -0.11, respectively; r² = 0.635).

Conclusions

These findings suggest that c-TTR associates with proactive strategies aimed at keeping patients very close to their target INR with a prompt re-evaluation of those patients with under- or over-therapeutic INR.

Quality of Anticoagulation With Vitamin K Antagonists

BACKGROUND

Vitamin K antagonists (VKA) have a narrow therapeutic range, and literature analysis reveals poor quality of anticoagulation control. We sought to assess the prevalence of poor anticoagulant control in patients under VKA treatment in the prevention of stroke for atrial fibrillation (AF).

HYPOTHESIS

Control of anticoagulation with VKA is inadequate in a high percentage of patients with AF.

METHODS

Patients with AF under VKA treatment were prospectively recruited in this observational registry. The sample comprised 948 patients. The estimated time spent in the therapeutic range (TTR) was calculated, and variables related with a TTR >65% were analyzed.

RESULTS

Mean age was 73.8 ± 9.4 years, and 42.5% of the patients were women. Mean TTR was 63.77% ± 23.80% for the direct method and 60.27% ± 24.48% for the Rosendaal method. Prevalence of poor anticoagulation control was 54%. Variables associated with good anticoagulation control were university studies (odds ratio [OR]: 1.99, 95% confidence interval [CI]: 1.08-3.64), chronic hepatic disease (OR: 8.15, 95% CI: 1.57-42.24), low comorbidity expressed as Charlson index (OR: 0.87, 95% CI: 0.76-0.99), no previous cardiac disease (OR: 0.64, 95% CI: 0.41-0.98), lower risk of bleeding assessed as hypertension, abnormal renal/liver function, stroke, bleeding history or predisposition, labile international normalized ratio, elderly age, and use of drugs or alcohol (HAS-BLED; OR: 0.81, 95% CI: 0.69-0.95), and lower heart rate (OR: 0.99, 95% CI: 0.98-0.99).

CONCLUSIONS

Patients who receive VKA to prevent stroke for AF spend less than half the time within therapeutic range.

Quality of vitamin K antagonist control and outcomes in atrial fibrillation patients: a meta-analysis and meta-regression

BACKGROUND

Atrial fibrillation (AF) patients frequently require anticoagulation with vitamin K antagonists (VKAs) to prevent thromboembolic events, but their use increases the risk of hemorrhage. We evaluated time spent in therapeutic range (TTR), proportion of international normalized ratio (INR) measurements in range (PINRR), adverse events in relation to INR, and predictors of INR control in AF patients using VKAs.

METHODS

We searched MEDLINE, CENTRAL and EMBASE (1990-June 2013) for studies of AF patients receiving adjusted-dose VKAs that reported INR control measures (TTR and PINRR) and/or reported an INR measurement coinciding with thromboembolic or hemorrhagic events. Random-effects meta-analyses and meta-regression were performed.

RESULTS

Ninety-five articles were included. Sixty-eight VKA-treated study groups reported measures of INR control, while 43 studies reported an INR around the time of the adverse event. Patients spent 61% (95% CI, 59-62%), 25% (95% CI, 23-27%) and 14% (95% CI, 13-15%) of their time within, below or above the therapeutic range. PINRR assessments were within, below, and above range 56% (95% CI, 53-59%), 26% (95% CI, 23-29%) and 13% (95% CI, 11-17%) of the time. Patients receiving VKA management in the community spent less TTR than those managed by anticoagulation clinics or in randomized trials. Patients newly receiving VKAs spent less TTR than those with prior VKA use. Patients in Europe/United Kingdom spent more TTR than patients in North America. Fifty-seven percent (95% CI, 50-64%) of thromboembolic events and 42% (95% CI, 35 - 51%) of hemorrhagic events occurred at an INR <2.0 and >3.0, respectively; while 56% (95% CI, 48-64%) of ischemic strokes and 45% of intracranial hemorrhages (95% CI, 29-63%) occurred at INRs <2.0 and >3.0, respectively.

CONCLUSIONS

Patients on VKAs for AF frequently have INRs outside the therapeutic range. While, thromboembolic and hemorrhagic events do occur patients with a therapeutic INR; patients with an INR <2.0 make up many of the cases of thromboembolism, while those >3.0 make up many of the cases of hemorrhage. Managing anticoagulation outside of a clinical trial or anticoagulation clinic is associated with poorer INR control, as is, the initiation of therapy in the VKA-naïve. Patients in Europe/UK have better INR control than those in North America.

Oral anticoagulant therapy and clinical outcomes in patients with atrial fibrillation: a pilot study from a single center registry

The data on the successful use of oral anticoagulation (OAC) in patients with atrial fibrillation are inconclusive. We aimed to describe the indications and the utilization patterns of OAC therapy in patients with atrial fibrillation who have been admitted to a quaternary hospital. Patients who were admitted to a quaternary hospital from January 2011 to January 2012 with atrial fibrillation were included in the study. The data on patient demographics, atrial fibrillation classification, CHA2DS2VASc scores, and the use of OAC were collected. Of the patients admitted, 301 patients met the inclusion criteria. Of these, 277 (92%) had a CHA2DS2VASc score at least 2. Of the patients who met criteria for treatment with OAC, 104 (36.6%) were not on OAC therapy. The reason for this discrepancy was tendency and history of bleeding (29.8%). Of those 180 patients who were on OAC, the time in therapeutic range was higher in those patients less than 50 years as compared with those between ages 65-74 and more than 75 (78.2 versus 42 and 36.1%, P < 0.05). The overall time in therapeutic range of patients on OAC was 47.4%. We found that approximately one-third of the patients who have indications for OAC are not being treated as per guidelines due to history of and tendency for bleeding. Furthermore, of those on OAC, only half of the patients achieved successful anticoagulation.

Cost-effectiveness of rivaroxaban compared with enoxaparin plus a vitamin K antagonist for the treatment of venous thromboembolism

BACKGROUND

Venous thromboembolism (VTE), comprised of deep vein thrombosis (DVT) and pulmonary embolism (PE), is commonly treated with a low-molecular-weight heparin such as enoxaparin plus a vitamin K antagonist (VKA) to prevent recurrence. Administration of enoxaparin + VKA is hampered by complexities of laboratory monitoring and frequent dose adjustments. Rivaroxaban, an orally administered anticoagulant, has been compared with enoxaparin + VKA in the EINSTEIN trials. The objective was to evaluate the cost-effectiveness of rivaroxaban compared with enoxaparin + VKA as anticoagulation treatment for acute, symptomatic, objectively-confirmed DVT or PE.

METHODS

A Markov model was built to evaluate the costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratios associated with rivaroxaban compared to enoxaparin + VKA in adult patients treated for acute DVT or PE. All patients entered the model in the 'on-treatment' state upon commencement of oral rivaroxaban or enoxaparin + VKA for 3, 6, or 12 months. Transition probabilities were obtained from the EINSTEIN trials during treatment and published literature after treatment. A 3-month cycle length, US payer perspective ($2012), 5-year time horizon and a 3% annual discount rate were used.

RESULTS

Treatment with rivaroxaban cost $2,448 per-patient less and was associated with 0.0058 more QALYs compared with enoxaparin + VKA, making it a dominant economic strategy. Upon one-way sensitivity analysis, the model's results were sensitive to the reduction in index VTE hospitalization length-of-stay associated with rivaroxaban compared with enoxaparin + VKA. At a willingness-to-pay threshold of $50,000/QALY, probabilistic sensitivity analysis showed rivaroxaban to be cost-effective compared with enoxaparin + VKA approximately 76% of the time.

LIMITATIONS

The model did not account for the benefits associated with an oral and minimally invasive administration of rivaroxaban. 'Real-world' applicability is limited because data from the EINSTEIN trials were used in the model. Also, resource utilization and costs were based on the US healthcare system.

CONCLUSION

Rivaroxaban is a cost-effective option for anticoagulation treatment of acute VTE patients.

Rivaroxaban in atrial fibrillation

Warfarin is the traditional therapeutic option available to manage thromboembolic risk in atrial fibrillation. The hemorrhagic risk with warfarin depends mainly on the international normalized ratio (INR). Data from randomized controlled trials show that patients have a therapeutic INR (2.00-3.00) only 61%-68% of the time while taking warfarin, and this target is sometimes hard to establish. Many compounds have been developed in order to optimize the profile of oral anticoagulants. We focus on one of them, rivaroxaban, comparing it with novel alternatives, ie, dabigatran and apixaban. The indication for rivaroxaban in nonvalvular atrial fibrillation was evaluated in ROCKET-AF (Rivaroxaban-once daily, Oral, direct factor Xa inhibition Compared with vitamin K antagonism for prevention of stroke and Embolism Trial in Atrial Fibrillation). In this trial, rivaroxaban was associated with a 12% reduction in the incidence of the primary endpoint compared with warfarin (hazard ratio 0.88; 95% confidence interval [CI] 0.74-1.03; P < 0.001 for noninferiority and P = 0.12 for superiority). However, patients remained in the therapeutic range for INR only 55% of the time, which is less than that in RE-LY (the Randomized Evaluation of Long-Term Anticoagulation Therapy, 64%) and in the ARISTOTLE trial (Apixaban for Reduction in Stroke and Other Thromboembolic Events in Atrial Fibrillation, 66%). This shorter time spent in the therapeutic range has been one of the main criticisms of the ROCKET-AF trial, but could actually reflect what happens in real life. In addition, rivaroxaban exhibits good pharmacokinetic and pharmacoeconomic properties. Novel anticoagulants are a viable and commercially available alternative to vitamin K antagonists nowadays for the prevention of thromboembolic complications in atrial fibrillation. Rivaroxaban is an attractive alternative, but the true picture of this novel compound in atrial fibrillation will only become available with more widespread use.

Current and future alternatives to warfarin for the prevention of stroke in atrial fibrillation

Atrial fibrillation (AF) is the most common sustained arrhythmia in clinical practice and is associated with a nearly 5-fold increase in the risk of stroke. Warfarin has been the cornerstone of treatment to reduce stroke risk in AF patients for decades. Although effective in preventing thrombosis, warfarin is difficult to manage and is associated with a 1% to 7% yearly risk of major hemorrhage. Until recently, there were no effective oral alternatives to warfarin. Dabigatran etexilate, a direct thrombin inhibitor, was approved in 2010 for the reduction of stroke and systemic embolism in patients with nonvalvular AF, and the factor Xa inhibitor rivaroxaban was approved for a similar indication in 2011. Other late-stage orally administered agents that may be approved for this indication include apixaban and edoxaban; others at earlier stages of development will be discussed in this review as well. Nonpharmacological approaches to stroke prevention include left atrial appendage removal, ligation, or occlusion. This review examines advances in the management of stroke risk in AF patients, focusing on recently marketed and late-stage modalities. The advent of alternatives to warfarin for reducing stroke risk in AF patients may improve physicians' ability to offer safe and effective stroke prevention in all AF patients.

Anticoagulation patient self-monitoring in the United States: considerations for clinical practice adoption

Systematic management models such as anticoagulation clinics have emerged in order to optimize warfarin effectiveness and to minimize related complications. Most of these models are structured so that patients come to a clinic for in-person testing and evaluation, thus making this model of care difficult to access and time consuming for many patients. The emergence of portable instruments for measuring anticoagulant effect in capillary whole blood made it possible for patients receiving warfarin to self-monitor the effect of their anticoagulant therapy. Self-monitoring empowers patients, offers the advantage of more frequent monitoring, and increases patient convenience by allowing testing at home and avoiding the need for frequent laboratory and clinic visits. Self-monitoring can entail patient self-testing (PST) and/or patient self-management (PSM). Several studies have evaluated and shown the benefit of both PST and PSM models of care when compared with either routine medical care or anticoagulation clinic management of anticoagulation therapy. Self-monitoring (PSM and/or PST) of anticoagulation results in lower thromboembolic events, lower mortality, and no increase in major bleeding when compared with standard care. Despite favorable results and enhanced patient convenience, the adoption of self-monitoring into clinical practice in the United States has been limited, especially in higher risk, disadvantaged populations. Although the emergence of a multitude of novel oral anticoagulants will permit clinicians to better individualize anticoagulant therapy options by choosing the optimum regimen based on individual patient characteristics, it is also expected that traditional agents will continue to play a role in a significant subset of patients. For those patients treated with traditional anticoagulants such as warfarin, future models of care will entail patient-centered management such as PST and PSM. The incorporation of technology (i.e., Web-based expert systems) is expected to further improve the outcomes realized by PST and PSM. Further studies are needed to explore factors that influence the adoption of self-monitoring in the United States and to evaluate the feasibility and implementation in real-life clinical settings.

Effectiveness of pharmacist-participated warfarin therapy management: a systematic review and meta-analysis

OBJECTIVE

Although pharmacist-participated warfarin therapy management (PWTM) has been accepted and implemented in various parts of the world, the evidence demonstrating the effects of PWTM compared with usual care on clinical outcomes is lacking. We performed a systematic review and meta-analysis to compare the effects of PWTM with usual care on bleeding and thromboembolic outcomes.

METHODS

We searched MEDLINE, SCOPUS, EMBASE, IPA, CINAHL, Cochrane CENTRAL, Thai Index Medicus and Thai Medical Index, and reference lists of studies, without language restriction. Databases were searched from their inception to July 2009. The studies using warfarin as an anticoagulant with sufficient data for compilation of 2 × 2 tables were included. Both randomized controlled trials (RCTs) and non-RCTs were considered. Two authors independently reviewed each study, assigned quality scores and extracted data for all outcomes using a standardized form. Pooled effect estimates (risk ratio; RR) were obtained using a random effects model.

RESULT

Of 661 articles identified, 24 studies with 728,377 patients were included. In the random-effects meta-analysis of RCTs, the PWTM group had statistically significant effects on the prevention of total bleeding [RR, 0.51; 95% confidence interval (CI), 0.28-0.94]. However, the effects on major bleeding (RR, 0.64; 95% CI, 0.18-2.36), thromboembolic events (RR, 0.79; 95% CI, 0.33-1.93), all-cause mortality (RR, 0.93; 95% CI, 0.41-2.13) and warfarin-related mortality (RR, 0.65; 95% CI, 0.18-2.42) were not significant.

CONCLUSION

Pharmacist's participation in the management of warfarin therapy significantly reduces total bleeding, with a non-significant trend towards decreases in other warfarin-related complications.

Prevalence of significant neoplasia in FOBT-positive patients on warfarin compared with those not on warfarin

OBJECTIVES

The fecal occult blood test (FOBT) is widely used for colorectal cancer screening. However, the impact of warfarin use on FOBT sensitivity and specificity remains unclear. This study compares the relative risk of neoplasia in FOBT-positive patients stratified by warfarin use.

METHODS

The Clinical Outcomes Research Initiative database was used to identify patients with positive FOBT as the only indication for colonoscopy during 2005-2006. Patients were categorized on the basis of documented warfarin status within a 30-day period before FOBT. We compared the demographics and prevalence of significant colon findings (defined as polyp >9 mm or suspected malignant tumor) among the two groups. After adjusting for confounding variables, logistic regression was used to estimate the odds ratio of significant findings in warfarin-positive vs. warfarin-negative patients.

RESULTS

Of 10,266 patients with positive FOBT, 372 used warfarin, 9,265 did not use warfarin, and 629 were excluded because of missing warfarin status. Warfarin-positive patients were more likely male (65 vs. 50%; P<0.0001), Caucasian (88 vs. 80%; P<0.0001), and veterans (53 vs. 33%; P<0.0001). The prevalence of a significant finding was greater in the warfarin group, 16 vs. 11.4% (P<0.01). After adjusting for age and sex, the relative risk of significant colon findings among warfarin-positive patients was not significantly different from warfarin-negative patients (odds ratio 1.1, 95% confidence interval: 0.81-1.44).

CONCLUSIONS

No increased risk for significant colonic findings among FOBT-positive patients according to warfarin use was identified. These findings suggest that continuing warfarin before FOBT will not affect the positive predictive value of this screening test.

10 years of oral anticoagulant pharmacogenomics: what difference will it make? A critical appraisal

Since the first report on warfarin pharmacogenetics in 1999, genetic variants have emerged as an important predictor of warfarin maintenance doses before therapy is initiated, raising expectations of greatly improved clinical outcomes. However, much of the information on warfarin sensitivity conveyed by genetic variants is captured by early international normalized ratio values traditionally used to guide dose titration. Thus, inclusion of early international normalized ratios in prediction models reduces the contribution of genetics. Moreover, in large population cohorts, genetics explained only 20–30% of variance in warfarin doses. Finally, even pharmacogenetic prediction models did not predict doses reliably in the majority of at-risk patients with warfarin requirements at the low or high end of the dose range. Currently, the clinical utility and cost–effectiveness of pharmacogenetic-based dosing are being assessed in large prospective trials in various settings. In the interim, enthusiasm for warfarin pharmacogenetics should not supersede strict adherence to traditional measures used to optimize coumarin anticoagulation.