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. 2017 Oct;63(10):e425-e431.

Time in therapeutic range: Warfarin anticoagulation for atrial fibrillation in a community-based practice

Derek Gateman  1 , Melissa Elizabeth Trojnar  2 , Gina Agarwal  3
Affiliations

Time in therapeutic range: Warfarin anticoagulation for atrial fibrillation in a community-based practice

Derek Gateman et al. Can Fam Physician. 2017 Oct.

Abstract
in English, French

Objective: To evaluate the effectiveness of an outpatient, nurse-administered warfarin anticoagulation protocol for the treatment of atrial fibrillation, and to identify clinical or biographical data that predict poor international normalized ratio control.

Design: Retrospective cohort study.

Setting: St Paul Family Health Network in Brantford, Ont.

Participants: A total of 150 patients with nonvalvular atrial fibrillation.

Main outcome measures: Time in therapeutic range (TTR) for each patient and for the clinic overall. The groups of patients above and below a target TTR of 60% were compared by stepwise binomial logistic regression.

Results: A time-weighted average TTR for the clinic was determined to be 58.76%, based on 183 452 patient-days taking warfarin. The regression analysis did not find a statistically significant association between TTR and any predictors. A trend indicating a 5-fold increase in the odds of inadequate anticoagulation was observed in current smokers (odds ratio of 4.71; 95% CI 0.97 to 22.93).

Conclusion: Compared with data from prospective randomized trials and meta-analysis, the anticoagulation protocol employed at the St Paul Family Health Network produced an average TTR near the lower end of the target threshold. Current smokers might be at greater risk of being below this target.

Objectif: Évaluer l’efficacité d’un protocole d’anticoagulation administré par des infirmières et qui utilise la warfarine comme traitement de la fibrillation auriculaire (FA); et identifier les facteurs cliniques et individuels qui prédisposent à un mauvais contrôle du RIN.

Type d’étude: Une étude de cohorte rétrospective.

Contexte: Le St Paul Family Health Network à Brantford, en Ontario.

Participants: Un total de 150 patients présentant une FA non valvulaire.

Principaux paramètres à l’étude: Un RIN dans la fourchette thérapeutique pour chaque patient et pour l’ensemble de la clinique. Les groupes de patients qui avaient des valeurs supérieures ou inférieures au RIN cible de 60 % ont été comparés étape par étape à l’aide d’une régression logistique binomiale.

Résultats: En se basant sur 183 452 jours-patients traités à la warfarine, on a calculé que le RIN avait une moyenne pondérée dans le temps de 58,76 % pour l’ensemble de la clinique. L’analyse de régression n’a pas révélé d’association significative entre le RIN et un autre facteur. On a observé une tendance indiquant que les fumeurs actifs avaient 5 fois plus de chances d’avoir une anticoagulation inadéquate (rapport de cotes 4.71; IC à 95 % 0.97 à 22.93).

Conclusion: En comparaison avec les données de méta-analyses et d’essais randomisés prospectifs, le protocole d’anticoagulation utilisé au St Paul Family Health Network a résulté en un RIN près de la limite inférieure de la valeur cible. Les fumeurs actifs pourraient être plus susceptibles d’avoir une valeur inférieure à cette cible.

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Figures

Figure 1.
Figure 1.
Case recruitment AF—atrial fibrillation, VTE—venous thromboembolism.
Figure 2.
Figure 2.
Linear interpolation example INR—international normalized ratio.
Figure 3.
Figure 3.
Frequency histogram of time-in-therapeutic-range values
Figure 4.
Figure 4.
Effect of predictors expressed as ORs with 95% CIs OR—odds ratio.
See this image and copyright information in PMC

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