Elsevier

Thrombosis Research

Volume 136, Issue 2, August 2015, Pages 216-220
Thrombosis Research

Regular Article
Warfarin treatment quality is consistently high in both anticoagulation clinics and primary care setting in Sweden

https://doi.org/10.1016/j.thromres.2015.04.016Get rights and content

Highlights

  • Retrospective cohort study on warfarin quality in Sweden.

  • Anticoagulation clinics (ACC) and primary health care centres (PHCC) compared.

  • In total 77.058 patients corresponding to 217.058 treatment years included.

  • TTR was significantly higher in PHCC compared to ACC (79.6% vs. 75.7%, p < 0.001).

  • No significant difference was seen in risk of overall complications.

Abstract

Background

Warfarin treatment in Sweden holds a high standard with time in therapeutic range (TTR) over 75%. Internationally, specialized anticoagulation clinics (ACC) have shown higher TTR compared to primary health care centres (PHCC).

Objectives

To compare warfarin treatment quality in Sweden for ACC versus PHCC, thereby clarifying whether centralization is for the better.

Patients/methods

In total 77.058 patients corresponding to 217.058 treatment years with warfarin in the Swedish national quality register AuriculA from 1. Jan 2006 to 31. Dec 2011. Information regarding TTR was calculated from AuriculA, while patient characteristics and complications were retrieved from the Swedish National Patient Register.

Results

Of the 100.554 treatment periods examined, 78.7% were monitored at ACC. Mean TTR for INR 2-3 for all patients irrespective of intended target range was 76.5% with an annual risk of bleeding or thrombotic events of 2.24% and 2.66%, respectively. TTR was significantly higher in PHCC compared to ACC (79.6% vs. 75.7%, p < 0.001), with no significant difference in overall risk of complications. Treatment periods for atrial fibrillation, except intended direct current conversion, showed similar results between ACC and PHCC without significant difference in annual risk of bleeding (2.50% vs. 2.51%) or thrombosis (3.09% vs. 3.16%). After propensity score matching there was still no significant difference in complication risk found.

Conclusions

Warfarin treatment quality is consistently high in both ACC and PHCC when monitored through AuriculA in Sweden, both measured as TTR and as risk of complications. In this setting, centralized warfarin monitoring is not likely to improve the results.

Introduction

In Sweden about 2 % of the population are treated with warfarin [1], [2]. Warfarin treatment is highly efficient, preventing death or recurrent pulmonary embolism (PE) in every second PE patient [3]. The most common indication for warfarin treatment is primary or secondary prevention of ischemic stroke in patients with atrial fibrillation (AF) [1], [2], [4], [5]. For patients with AF with one or more risk factors for stroke (heart failure, hypertension, diabetes, age over 75 years, prior stroke), the annual risk of a stroke is between 2 and 18%. Treatment with oral anticoagulants can reduce the risk of stroke by 2/3 [6].

At the same time, treatment with oral anticoagulants confers a significant risk of severe bleeding [6]. In recent years warfarin has topped the Medical Products Agencies list of products linked to serious side effects in Sweden [7]. This despite the fact that repeated studies have shown that the warfarin treatment quality in Swedish centres is of a very high standard [8], [9], [10].

Warfarin dosing requires an experienced staff and a well-structured organization to function optimally. The quality of the treatment can be measured either directly by the frequency of bleeding and thromboembolic events, or indirectly by measuring to what proportion of the treatment time the patients were in the planned therapeutic range, "Time in Therapeutic Range", TTR [11]. A high TTR has been shown to correlate with a low risk of bleeding or thromboembolic events [12], [13], [14], but also other factors like health care organization are likely to influence the patient´s outcome.

TTR is a simple quality measurement which in computer-based dosing systems can be directly reported back to each participating centre, while the clinical outcomes like frequencies of bleeding, thromboembolic events or death are more difficult to retrieve and requires a longer follow-up. Previous studies of quality differences in warfarin treatment between anticoagulation clinics (ACC) and primary health care centers (PHCC) expressed in clinical outcome like frequencies of complications are few worldwide, but one performed in northern Sweden has shown no significant differences in bleeding frequency with 4.1 % per treatment year for ACC and 3.9 % for PHCC [8].

The aim of this study is to compare the warfarin treatment quality in ACC and PHCC in Sweden, expressed as TTR and frequency of complications, to evaluate whether the centralization of these patients is for the better.

Section snippets

AuriculA

AuriculA is a Swedish national quality register for AF and oral anticoagulation, which since 2008 is funded by the Swedish Association of Local Authorities and Regions. The register started in 2006, and now includes over 110.000 patients from 224 participating centers nationwide, both ACC as well as PHCC. Approximately 50% of all patients on warfarin in Sweden are included in AuriculA. Participation in AuriculA is mostly within whole regions with no apparent selection bias. Over 5.000.000 INR

Results

In total 77.058 patients with 100.554 treatment periods corresponding to 217.058 treatment years were examined. For 72.267 treatment periods, the patient had been to a hospital prior to starting warfarin, and thus had information regarding background characteristics in NPR (Table 1). Of all treatment periods 79.107 (78.7%) were managed in ACC and 21.447 (21.3%) in PHCC.

Patients managed in PHCC were older than those in ACC, 73.4 vs. 69.8 years (p < 0.001). Treatment indications were similar

Discussion

In a large real life cohort of 77.058 patients and 100.554 warfarin treatment periods, we show a high mean TTR of 76.5%. By way of comparison, clinical randomized controlled trials with selected centers and patients as well as monitors who follow up their treatment report a TTR between 55 and 64% [13], [20]. In clinical practice, specialist clinics in the United States have shown a TTR of 63% and American public health centers only 51% [21], raising a question whether centralisation of warfarin

Limitations

Although this is a relatively large study, including almost 80.000 patients, it has a retrospective observational design based purely on data retrieved from medical records and registries, which are limited by the accuracy of completeness of documentation. The validity in the NPR is however good. In somatic care, the register lacks information about primary diagnosis in only 0.5-0.9% of hospital admissions [23].

There is a lack of baseline characteristics for those patients not included in the

Conclusion

Warfarin treatment quality is consistently high in both ACC and PHCC when monitored through AuriculA in Sweden, both measured as TTR and as risk of complications. In this setting, centralized warfarin monitoring is not likely to improve the results.

Ethical Approval

This study was approved by the regional ethical review board in Umeå, Sweden (EPN nr 2011-349-31 M and 2014-191-32 M) and conformed to the declaration of Helsinki.

Contributors

AS and PJS designed the study. AS, FB, HR and PS extracted and analysed data. FB, PS and AS drafted the manuscript. All authors critically reviewed the manuscript, contributed to its revision, and approved the final version submitted.

Funding

This study was supported by the Department of Public Health and Clinical Medicine, Umeå University and the Department of Research and Development, County Council of Vasternorrland [LVNFOU216571, 310871, 385111].

Conflict of Interest Statement

None

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