Can We Predict Daily Adherence to Warfarin? Results From the International Normalized Ratio Adherence and Genetics (IN-RANGE) Study

MSCE, University of Pennsylvania School of Medicine, 707 Blockley Hall, 423 Guardian Dr, Philadelphia, PA 19104-6021, USA.
Chest (Impact Factor: 7.48). 11/2009; 137(4):883-9. DOI: 10.1378/chest.09-0039
Source: PubMed


Warfarin is the primary therapy to prevent stroke and venous thromboembolism. Significant periods of nonadherence frequently go unreported by patients and undetected by providers. Currently, no comprehensive screening tool exists to help providers assess the risk of nonadherence at the time of initiation of warfarin therapy.
This article reports on a prospective cohort study of adults initiating warfarin therapy at two anticoagulation clinics (university- and Veterans Affairs-affiliated). Nonadherence, defined by failure to record a correct daily pill bottle opening, was measured daily by electronic pill cap monitoring. A multivariable logistic regression model was used to develop a point system to predict daily nonadherence to warfarin.
We followed 114 subjects for a median of 141 days. Median nonadherence of the participants was 14.4% (interquartile range [IQR], 5.8-33.8). A point system, based on nine demographic, clinical, and psychosocial factors, distinguished those demonstrating low vs high levels of nonadherence: four points or fewer, median nonadherence 5.8% (IQR, 2.3-14.1); five points, 9.1% (IQR, 5.9-28.6); six points, 14.5% (IQR, 7.1-24.1); seven points, 14.7% (IQR, 7.0-34.7); and eight points or more, 29.3% (IQR, 15.5-41.9). The model produces a c-statistic of 0.66 (95% CI, 0.61-0.71), suggesting modest discriminating ability to predict day-level warfarin nonadherence.
Poor adherence to warfarin is common. A screening tool based on nine demographic, clinical, and psychosocial factors, if further validated in other patient populations, may help to identify groups of patients at lower risk for nonadherence so that intensified efforts at increased monitoring and intervention can be focused on higher-risk patients.

Download full-text


Available from: Maureen Price,
  • Source
    • "Warfarin is effective when the therapeutic range is maintained, but when the levels are below or above the intended range, it is associated with increased risk of thrombosis and bleeding, respectively (Hylek et al., 1996). Poor adherence to warfarin is common with one in five doses taken incorrectly even in the setting of a dedicated anticoagulation clinic (Platt et al., 2010). A study showed that up to 92% of the patients could not adhere to warfarin therapy and had under anticoagulation control. "
    [Show abstract] [Hide abstract]
    ABSTRACT: Warfarin is a commonly prescribed oral anticoagulant in Saudi Arabia and yet patient adherence to warfarin therapy and its impact on anticoagulation control have not been well researched here. A cross-sectional survey was conducted over 6 weeks at the outpatient anticoagulant clinic on patients who were receiving warfarin. Adherence was assessed using the translated Arabic version of the Morisky Medication Adherence Scale (MMAS-8). Levels of adherence were classed as low (score ⩽ 7), or high (score = 8) based on the scores. Good anticoagulation control was defined as percent Time INR in Therapeutic Range (TTR) ⩾ 75% using the Rosendaal method. A total of 192 patients completed a questionnaire with a response rate of 68.1%. It was established that no association was found between adherence to warfarin therapy and INR control groups. Among the 89 (46.4%) patients who had high adherence, only 34 (38.2%) had an acceptable INR control. This was versus 103 (53.6%) patients who had low adherence but also 34 (33.0%) had good INR control. Multivariate logistic regression (MLR) analysis showed that when studying females and occupational status of unemployment, they were independently associated with poor INR control with an OR 2.31, 95% CI 1.10–4.92, and OR 2.71, 95% CI 1.12–6.61 respectively. MLR analysis also showed that age <50 years alongside no formal education was independently associated with low adherence to warfarin therapy with an OR 2.67, 95% CI 1.29–5.52 and OR 2.63, 95% CI 1.01–6.93 respectively. The demographic background influences adherence and INR control, but no association was found between adherence and anticoagulation control.
    Saudi Pharmaceutical Journal 02/2015; 2014. DOI:10.1016/j.jsps.2015.02.005 · 1.28 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Vorhofflimmern ist die häufigste Herzrhythmusstörung bei geriatrischen Patienten, die Prävalenz bei über 80-Jährigen beträgt etwa 10%. Patienten mit Vorhofflimmern haben ein doppelt so hohes Mortalitätsrisiko, das Risiko für einen Schlaganfall ist um den Faktor 5 erhöht. Im Gegensatz dazu stehen die aktuellen Leitlinien der Europäischen Kardiologischen Gesellschaft (ESC), die diese Patientengruppe kaum berücksichtigen. Insbesondere mangelt es an Empfehlungen zu alltäglichen Fragen in der klinischen Betreuung dieser Patientengruppe. Ziel der vorliegenden Arbeit ist, für geriatrisch tätige Kolleg(inn)en unter Aufarbeitung der spezifischen Fachliteratur die vorliegende europäische Leitlinie für dieses Patientenkollektiv zu ergänzen. Diskutiert werden die Themenbereiche Rhythmus- versus Frequenzkontrolle, Antikoagulation, Outcome und Prävention, Stürze, Compliance/Adhärenz, Polypharmazie, geriatrisches Assessment, Demenz, Pflegeheimpatienten und Frailty nach Literaturrecherche in PubMed in Hinblick auf den geriatrischen Patienten. Individuelle Aspekte sollten in die Therapiegestaltung einfließen, allerdings darf die Komplexität dieser Patienten nicht zu einer bedingungslosen Individualisierung der Therapie abseits der Leitlinien führen. Denn es gibt zahlreiche Literaturstellen, mit denen sich viele offene Fragen im Zusammenhang mit Vorhofflimmern bei geriatrischen Patienten beantworten lassen.
    Zeitschrift für Gerontologie + Geriatrie 01/2012; 45(1). DOI:10.1007/s00391-011-0268-0 · 0.81 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Thromboembolism is the main cause of death and disability of patients with atrial fibrillation. Indirect anticoagulants are effective means of primary and secondary prevention of thromboembolic complications. However in a number of patients risk associated with therapy with indirect anticoagulants might exceed potential benefit. The principle problem requiring solution in a patient with atrial fibrillation is individual comparative assessment of risk of development of thromboembolic and hemorrhagic complications. Modern stratification scales which allow solving this problem are considered in this review.
    Kardiologiia 01/2011; 51(10):81-91. · 0.12 Impact Factor
Show more