Evaluation of the impact of warfarin time in therapeutic range on outcomes of patients with atrial fibrillation in Turkey: perspectives from the observational, prospective WATER Registry

Anticoagulation Management in Patients Receiving Warfarin at Private Cardiac Centers in Addis Ababa, Ethiopia

Introduction

Anticoagulants are the cornerstone therapy for thromboembolism prevention and treatment. Warfarin is the frequently prescribed drug and remains the oral anticoagulant of choice in low- and middle-income countries, including Ethiopia. It is a narrow therapeutic index drug that needs high-quality anticoagulation monitoring with frequent international normalization ratio (INR) testing.

Objective

The study aimed to assess anticoagulation management with warfarin among adult outpatients at two selected private cardiac centers in Addis Ababa, Ethiopia.

Methods

A hospital-based retrospective study design that enrolled 374 patients receiving warfarin was employed at two private cardiac centres in Addis Ababa, Ethiopia. The time in the therapeutic range (TTR) was calculated using the Rosendaal method. The data were analyzed using Statistical Package for Social Science version 25.

Results

The mean age of the patients was 57 years, and 218 (58.3%) participants were females. Out of 3384 INR tests, 1562 (46.5%) were within the therapeutic range and the mean percentage of TTR was 47.24%. Only 25.67% of the patients spent their TTR ≥ 65%. The present study revealed that dose adjustments were required 1764 times. In non-therapeutic INR values of 1764 that required warfarin dose adjustment, 59.7% of the doses were adjusted. About 262 (70.1%) of co-prescribed medications had interaction with warfarin. Sixty-four patients (17.11%) experienced bleeding events.

Conclusion

Anticoagulation management with warfarin was suboptimal in private cardiac Addis Ababa, Ethiopia, private cardiac centers. Warfarin adjustment practice for nontherapeutic INR values was not minimal, and many patients encountered bleeding during their course of therapy.

Anticoagulation control, outcomes, and associated factors in long-term-care patients receiving warfarin in Africa: a systematic review

Background

Oral anticoagulation therapy with warfarin requires frequent monitoring level of anticoagulation by the international normalized ratio (INR). In Africa, studies that explore anticoagulation control, treatment outcomes, and associated factors are reported in various ways in long-term patients receiving warfarin therapy to generate concrete scientific evidence.

Methods

The literature search was conducted in PubMed, Cochrane Library, African Journal of Online databases, Google Scholar, and Google. An advanced search strategy was computed to retrieve relevant studies related to anticoagulation control and outcomes. Duplication, title and abstract screening, and full-text assessment were conducted in Covidence software. Study quality was assessed using the Joanna Briggs Institute Critical appraisal quality assessment tool. The systematic review is registered in PROSPERO (CRD42021260772) and performed based on the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA) guideline.

Results

Out of 298 identified articles, 18 articles were eligible for the final review and analysis. The mean of 39.4 ± 8.4% time in therapeutic range (TTR) (29.4 to 57.3%), 36.7 ± 11.5% TTR (range 25.2–49.7%) and 46% TTR (43.5–48.5%) was computed from studies that determined TTR by Rosendaal, direct and cross-section-of-the-files methods, respectively. In this review, the lowest percentage of TTR was 13.7%, while the highest was 57.3%. The highest percentage of patients (32.25%) who had TTR ≥ 65% was reported in Tunisia, but the lowest percentages were in Namibia (10%, TTR ≥ 65%) and Kenya (10.4%, TTR ≥ 70%). Most of the included studies (11 out of 18) used Rosendaal’s method while the direct method was employed by three studies. Generally, 10.4–32.3% of study participants achieved desired optimal anticoagulation level. Regarding secondary outcomes, 1.6–7.5% and 0.006–59% of patients experienced thromboembolic complications and bleeding events, respectively. Having chronic comorbidities, taking more than two drugs, and presence of medications that potentially interact with warfarin, and patient-related factors (patients aged < 50 years old, female gender, lower education level, smoking history) were the frequently reported predictors of poor anticoagulation therapy.

Conclusions

Oral anticoagulation control was suboptimal in patients taking warfarin as evidenced by low TTR in Africa. Therefore, there is an urgent need for further improving oral anticoagulation management services.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12959-022-00416-9.

Anticoagulation Control, Outcomes, and Associated Factors in Patients with Atrial Fibrillation Receiving Warfarin at Tertiary Care Hospital in Ethiopia

Anticoagulation is the cornerstone in the prevention of stroke in atrial fibrillation. This study aimed at assessing the anticoagulation control and outcome and predictive factors in atrial fibrillation patients on warfarin therapy. A retrospective chart review was used to evaluate patients with atrial fibrillation who were on warfarin during two years follow up at the anticoagulation clinic of the hospital. The time in therapeutic range (TTR) was calculated using Rosendaal's method. Data were analyzed using SPSS software version 25. Univariable and multivariable analyses were computed to determine factors affecting TTR and bleeding events. We included 300 patients in this study. The mean percentage TTR was 42.03 ± 18.75. Only 38 (12.67%) patients achieved a TTR of above 65%. The average international normalized ratio (INR) testing frequency was 35 days (16.3-67.2 days). Taking 1 or 2 drugs along with warfarin was found to be better in achieving good TTR as compared to taking more than two drugs (p = .014). Having heart failure was associated with a 2.45 times odds of poor anticoagulation control (TTR< 65%) (p = .047). Male study participants were 2.53 times more likely of developing bleeding events than females (p = .009). Bleeding events were observed in 62 (20.67%) patients. Study participants, who didn't have Diabetic Mellitus and those not receiving aspirin were at lower odds developing bleeding events (AOR = .196; C.I. = .060-.638; p−.007 and AOR = .099; CI. = .024-.416; p−.02), respectively. In summary, the time spent in the therapeutic range was minimal in this population of patients with AF on warfarin managed at a hospital run anticoagulation clinic in Ethiopia. Moreover, the number of co-prescribed medications, and having heart failure were associated with poor TTR. Bleeding events were high and affected by male sex, having DM comorbidity, and using aspirin.

Patient-related factors associated with oral anticoagulation control: a population-based cohort study

OBJECTIVES

Time in therapeutic range (TTR) of ≥70% is a commonly used indicator of optimal anticoagulation control. This study aimed to determine the patterns and predictors of anticoagulation control in a population-based cohort of new users of warfarin.

METHODS

This was a retrospective cohort study. All adults (age ≥18 years) who had been newly initiated on warfarin therapy between January 2006 and March 2011were selected from administrative health databases. TTR was calculated using the Rosendaal method. Multivariable logistic regression models were used to identify patient-related factors associated with optimal TTR. Predictors of patients spending >30% of time above and below the therapeutic international normalised ratio (INR) range were also examined.

KEY FINDINGS

A total of 6032 patients were included in this study. The mean TTR was 54.1 ± 18.8%, and 82.3% of patients had subthreshold TTR (<70%). Compared with New Zealand Europeans, Māori and Pacific people had decreased odds of achieving optimal TTR and increased odds of spending >30% of time below the therapeutic INR range. Patients aged 65-74 years and 75 years or older had increased odds of achieving optimal TTR but decreased odds of spending >30% of time below the therapeutic INR range than those <65 years. Compared with those living in the least socioeconomically deprived areas, those living in the most deprived areas had decreased odds of achieving optimal TTR.

CONCLUSIONS

Anticoagulation control with warfarin is suboptimal in routine care in New Zealand. Age, ethnicity and deprivation index were significant predictors of TTR. It is important to ensure equitable access to appropriate, high-quality care for those living in deprived areas and those from ethnic minority groups.

Evaluation of Bleeding Rate and Time in Therapeutic Range in Patients Using Warfarin Before and During the COVID-19 Pandemic-Warfarin Treatment in COVID-19

The treatment process of patients using warfarin is expected to be hindered during the COVID-19 pandemic. Therefore we investigated whether the time in therapeutic range (TTR) and bleeding complications were affected during the COVID-19 pandemic. 355 patients using warfarin were included between March 2019 to March 2021. Demographic parameters, INR (international normalized ratio), and bleeding rates were recorded retrospectively. The TTR value was calculated using Rosendaal’s method. The mean age of the patients was 61 ± 12 years and 55% of them were female. The mean TTR value during the COVID-19 pandemic was lower than the pre-COVID-19 period (56 ± 21 vs 68 ± 21, P < 0.001). Among the patients, 41% had a lack of outpatient INR control. During the COVID-19 pandemic, 71 (20%) patients using VKA suffered bleeding. Among patients with bleeding, approximately 60% did not seek medical help and 6% of patients performed self-reduction of the VKA dose. During the COVID-19 pandemic, TTR values have decreased with the lack of monitoring. Furthermore, the majority of patients did not seek medical help even in case of bleeding.

The Prevalence and Risks of Inappropriate Combination of Aspirin and Warfarin in Clinical Practice: Results From WARFARIN-TR Study

Background

The use of warfarin and aspirin in combination is restricted to limited patients under relevant guidelines.

Aims

To evaluate the prevalence of the inappropriate combination of aspirin and warfarin therapy in daily practice and its risks.

Study Design

Cross-sectional study.

Methods

The awareness, efficacy, safety, and time in the therapeutic range of warfarin in the Turkish population study is a multi-center observational study that includes 4987 patients using warfarin for any reason between January 1, 2014, and December 31, 2014. To determine the prevalence of inappropriate combination use in daily practice, all patients who had a history of atherosclerotic disease (ischemic heart disease, peripheral artery disease) or cerebrovascular disease (n=1498) were excluded. The data of 3489 patients were analyzed. We defined inappropriate combination as all patients who received aspirin and warfarin regardless of the indication for warfarin use, under the direction of the European Society of Cardiology guideline recommendation.

Results

The mean age of patients was 59.2±13.8 years (41.8% male). The prevalence of the inappropriate use of warfarin and aspirin combination was 20.0%. The prevalence of combination therapy in patients with a primary indication for mechanical heart valve, non-valvular atrial fibrillation, and other reasons was 20.5%, 18.7%, and 21.0%, respectively. Multivariate logistic regression analysis revealed that age (odds ratio, 1.009; 95% confidence interval, 1.002-1.015; p=0.010), heart failure (odds ratio, 1.765; 95% confidence interval, 1.448-2.151; p<0.001), smoking (odds ratio, 1.762; 95% confidence interval, 1.441-1.153; p<0.010), chronic kidney disease (odds ratio, 2.057; 95% confidence interval, 1.494-2.833; p<0.001), and deep vein thrombosis (odds ratio, 0.463; 95% confidence interval, 0.229-0.718; p=0.001) were independent predictors of combination therapy (r2=0.66). The mean time in therapeutic range of patients receiving combination therapy was significantly lower than in those on warfarin monotherapy (51.6±27.05 vs. 54.7±23.93; p=0.006). Overall, 19.4% (n=677) of patients had a bleeding event (major bleeding 13.0%, n=88) within a year. Percentages of patients with combination therapy were significantly higher in patients with major bleeding than in patients without major bleeding (29.5% vs. 19.7%; p=0.023).

Conclusion

Our study demonstrated that 20.0% of patients taking warfarin use concomitant aspirin inappropriately in daily practice. Patients receiving aspirin with warfarin were demonstrated to have more comorbidities, lower time in therapeutic range levels, and higher bleeding rates.

ReAl-life Multicenter Survey Evaluating Stroke prevention strategies in non-valvular atrial fibrillation (RAMSES study)

Objective:

Data regarding stroke prevention strategies in non-valvular atrial fibrillation (NVAF) are limited to vitamin K antagonists (VKAs). This study aimed to evaluate real-life stroke prevention strategies for NVAF patients in the era of non-VKA oral anticoagulants (NOACs).

Methods:

We established a cross-sectional, multicenter, nationwide registry of NVAF patients. All consecutive atrial fibrillation (AF) patients and without mechanical heart valves or rheumatic mitral stenosis (but including those with any degree of mitral regurgitation) were enrolled in the ReAl-life Multicenter Survey Evaluating Stroke Prevention Strategies (RAMSES Study; ClinicalTrials.gov identifier NCT02344901) in Turkey. Baseline demographic data, medical history, and medications prescribed for NVAF treatment were collected. Univariate analyses were performed for continuous variables, and the chi-square test was used for categorical variables.

Results:

In total, 6273 patients from 29 provinces of Turkey were enrolled in the study between February and May 2015, with the contribution of 83 investigators. The mean age was 69.6±10.7 years; 56% of the patients were females, and one-fifth of the patients had at least one comorbid disease, the most common being hypertension (69%). The mean CHA₂DS₂–VASc and HAS-BLED scores were 3.3±1.6 and 1.6±1.1, respectively. The rate of oral anticoagulant (OAC) therapy use was 72% (37% NOAC and 35% VKA).

Conclusion:

The RAMSES study showed a higher prevalence of OAC use among NVAF patients than that reported in previous studies. Although NOACs were preferred over VKAs in daily cardiology practice, there is a need for improved OAC therapies for NVAF patients.

The importance of mean time in therapeutic range for complication rates in warfarin therapy of patients with atrial fibrillation: A systematic review and meta-regression analysis

Background

\Anticoagulation is used for stroke prophylaxis in non-valvular atrial fibrillation, amongst other by use of the vitamin K antagonist, warfarin. Quality in warfarin therapy is often summarized by the time patients spend within the therapeutic range (percent time in therapeutic range, TTR). The correlation between TTR and the occurrence of complications during warfarin therapy has been established, but the influence of patient characteristics in that respect remains undetermined. The objective of the present papers was to examine the association between mean TTR and complication rates with adjustment for differences in relevant patient cohort characteristics.

Methods

A systematic literature search was conducted in MEDLINE and Embase (2005–2015) to identify eligible studies reporting on use of warfarin therapy by patients with non-valvular atrial fibrillation and the occurrence of hemorrhage and thromboembolism. Both randomized controlled trials and observational cohort studies were included. The association between the reported mean TTR and major bleeding and stroke/systemic embolism was analyzed by random-effects meta-regression with and without adjustment for relevant clinical cohort characteristics. In the adjusted meta-regressions, the impact of mean TTR on the occurrence of hemorrhage was adjusted for the mean age and the proportion of populations with prior stroke or transient ischemic attack. In the adjusted analyses on thromboembolism, the proportion of females was, furthermore, included.

Results

Of 2169 papers, 35 papers met pre-specified inclusion criteria, holding relevant information on 31 patient cohorts. In univariable meta-regression, increasing mean TTR was significantly associated with a decreased rate of both major bleeding and stroke/systemic embolism. However, after adjustment mean TTR was no longer significantly associated with stroke/systemic embolism. The proportion of residual variance composed by between-study heterogeneity was substantial for all analyses.

Conclusions

Although higher mean TTR in warfarin therapy was associated with lower complication rates in atrial fibrillation, the strength of the association was decreased when adjusting for differences in relevant clinical characteristics of the patient cohorts. This study suggests that mainly the safety of warfarin therapy increases with higher mean TTR, whereas effectiveness appears not to be substantially improved.

Due to the limitations immanent in the meta-regression methods, the results of the present study should be interpreted with caution. Further research on the association between the quality of warfarin therapy and risk of complications is warranted with adjustment for clinically relevant characteristics.

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.

The Time in Therapeutic Range and Bleeding Complications of Warfarin in Different Geographic Regions of Turkey: A Subgroup Analysis of WARFARIN-TR Study

Background:

The time in therapeutic range values may vary between different geographical regions of Turkey in patients vitamin K antagonist therapy.

Aims:

To evaluate the time in therapeutic range percentages, efficacy, safety and awareness of warfarin according to the different geographical regions in patients who participated in the WARFARIN-TR study (The Awareness, Efficacy, Safety and Time in Therapeutic Range of Warfarin in the Turkish population) in Turkey.

Study Design:

Cross-sectional study.

Methods:

The WARFARIN-TR study includes 4987 patients using warfarin and involved regular international normalized ratio monitoring between January 1, 2014 and December 31, 2014. Patients attended follow-ups for 12 months. The sample size calculations were analysed according to the density of the regional population and according to Turkish Statistical Institute data. The time in therapeutic range was calculated according to F.R. Roosendaal’s algorithm. Awareness was evaluated based on the patients’ knowledge of the effect of warfarin and food-drug interactions with simple questions developed based on a literature review.

Results:

The Turkey-wide time in therapeutic range was reported as 49.5%±22.9 in the WARFARIN-TR study. There were statistically significant differences between regions in terms of time in therapeutic range (p<0.001). The highest rate was reported in the Marmara region (54.99%±20.91) and the lowest was in the South-eastern Anatolia region (41.95±24.15) (p<0.001). Bleeding events were most frequently seen in Eastern Anatolia (41.6%), with major bleeding in the Aegean region (5.11%) and South-eastern Anatolia (5.36%). There were statistically significant differences between the regions in terms of awareness (p<0.001).

Conclusion:

Statistically significant differences were observed in terms of the efficacy, safety and awareness of warfarin therapy according to different geographical regions in Turkey.

Potential Causes and Implications of Low Target Therapeutic Ratio in Warfarin-Treated Patients for Thrombosis Prophylaxis: A Single-Center Experience

Time in therapeutic range (TTR) of international normalized ratio is crucial for the safety and efficacy of anticoagulation with warfarin and it is influenced by many factors. There are limited data about the quality of warfarin therapy and its effects on clinical outcomes in Turkey. The aim of this study is to demonstrate the quality of anticoagulant therapy with warfarin and evaluate the parameters that affect the quality of warfarin therapy. A total of 170 patients with atrial fibrillation (AF; mean age: 62.2 ± 13.3; 69.2% female) treated with warfarin were included in this study. The mean follow-up period was 20 ± 8.4 months. The mean TTR levels of all patients were found to be 54.2% ± 21.4%. The TTR levels were similar in patients with valvular AF (VAF) and nonvalvular AF (NVAF). Logistic regression analysis revealed that elderly, heart failure (HF), and renal dysfunction were independent predictors of lower TTR. There were no significant differences between the VAF and NVAF subgroups regarding the incidence of mortality, stroke, and myocardial infarction. Cox regression analysis revealed that HF, coronary artery disease, and renal dysfunction were independent predictors of clinical outcomes in addition to lower TTR. Our results provide data regarding the quality of anticoagulation with warfarin from a single tertiary center in Istanbul, Turkey. The questions remain in seeking quality improvement in anticoagulation.

Rivaroxaban vs. warfarin on extended deep venous thromboembolism treatment: A cost analysis

Background

Standard treatment for deep venous thromboembolism involves parenteral anticoagulation overlapping with a vitamin K antagonist, an approach that is effective but associated with limitations including the need for frequent coagulation monitoring. The direct oral anticoagulant rivaroxaban is similarly effective to standard therapy as a single-drug treatment for venous thromboembolism and does not require routine coagulation monitoring. The aim of this analysis was to project the long-term costs and outcomes for rivaroxaban compared to standard of care (tinzaparin/warfarin).

Methods

A total of 184 patients who were under anticoagulant therapy with warfarin or rivaroxaban for extended deep venous thromboembolism were retrospectively evaluated; 59 received rivaroxaban and 125 received warfarin therapy. Assessments were made on age, gender, place of residence, the duration of anticoagulation, mean international normalized ratio value, the effective rate of international normalized ratio (time in the therapeutic range), bleeding-related complication rate, duration of hospitalization due to complications, the number of annual outpatient department admission, cost for drug, cost for hospitalization, cost for outpatient department admission and international normalized ratio measurements.

Results

The annual outpatient cost is higher in warfarin group (147.09 ± 78 vs. 62.32 ± 19.79 USD p < 0.001). But annual drug cost is higher in rivaroxaban group (362.6 vs. 71.55 ± 31.01 USD p < 0.001). Overall cost of rivaroxaban group is higher than warfarin group (476.25 ± 36.78 vs. 364.82 ± 174.44 USD). Warfarin is not cost-effective when non-drug costs (342.5 ± 174.44 vs. 113.65 ± 36.77) and hospital costs (173.85 ± 122.73 vs. 64.9 ± 23.55 USD) were analyzed.

Conclusion

This analysis suggests that rivaroxaban has lower costs than warfarin in terms of outpatient department admission and hospital costs due to complications; however, warfarin was more economic when all cost parameters were considered. Time in the therapeutic range was found as 56% for warfarin that should be taken into account while analyzing costs and benefits.