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The quality of oral anticoagulant therapy and recurrent venous thrombotic events in the Leiden Thrombophilia Study
Author(s) -
GADISSEUR A. P. A.,
CHRISTIANSEN S. C.,
VAN DER MEER F. J. M.,
ROSENDAAL F. R.
Publication year - 2007
Publication title -
journal of thrombosis and haemostasis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.947
H-Index - 178
eISSN - 1538-7836
pISSN - 1538-7933
DOI - 10.1111/j.1538-7836.2007.02385.x
Subject(s) - medicine , thrombosis , thrombophilia , venous thrombosis , confidence interval , oral anticoagulant , anticoagulant , anticoagulant therapy , population , surgery , warfarin , atrial fibrillation , environmental health
Summary. Background: The International Normalized Ratio (INR) target range is a relatively narrow range in which the efficacy of oral anticoagulant treatment, i.e. prevention of extension and recurrence of thrombosis, is balanced with the risk of hemorrhagic complications. Over the years, different INR target ranges have been implemented for individual indications, depending on their thrombotic potential. In most of the studies defining these INR targets, the treatment of the patients was aimed at a certain INR range, but in the analysis no account was taken of the time that the patients spent within this range in reality. Methods: The Leiden Thrombophilia Study (LETS) is a population‐based case‐control study on risk factors for venous thrombosis, in which many genetic and acquired factors have been investigated. Our aim was to investigate the effect of the quality of the oral anticoagulant therapy for the initial venous thrombosis and its relationship with recurrence of thrombosis. Quality of anticoagulation was defined as the time spent at various INR levels during treatment, and we focused on the effect of sustained intensities above a certain INR in preventing recurrences later on. Results: Two hundred and sixty‐six patients with a total follow‐up of 2495 patient‐years were studied. The mean duration of the initial anticoagulant therapy was 194.5 days (range 48–4671). During follow‐up, 58 recurrences were diagnosed (cumulative recurrence rate of 21.8% over 9 years). The mean INR during initial therapy was 2.90, with 90.3% [95% confidence interval (CI) 88.4–92.3%] of the time being spent above an INR of 2.0, and 39.1% (95% CI 35.5–42.7%) above an INR of 3.0. Patients who spent more time below the target range, or who had a shorter duration of anticoagulation, did not experience a higher risk of recurrence after the initial period of anticoagulation had passed. Conclusion: Provided that oral anticoagulant treatment is adequately managed, according to international guidelines, recurrent thrombosis cannot be ascribed to variation in the primary treatment. Further attempts to reduce the risk of recurrence should therefore be aimed at identifying other explanatory factors, and subsequently fine‐tuning the target ranges.