Adherence of Apixaban and Warfarin in Patients With Arterial Fibrillation in Real-world Setting in Sweden

Study Overview
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Brief Summary
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This will be a retrospective cohort study using national register linkage data (including prescription, inpatient, mortality, and socioeconomic data). The study period will be from May 29, 2013 to June 30, 2015. Patients will be followed from the start of treatment (index date) until their death, exiting the database, or until the end of the study period (June 30, 2015).

Official Title
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Adherence of Apixaban and Warfarin in Patients With Atrial Fibrillation in Real-world Setting in Sweden

Conditions
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Anticoagulation

Participation Criteria
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Eligibility Criteria
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Inclusion Criteria: For the AF cohort Patients that have ≥1 AF diagnosis registered in the patient register Apixaban subcohort 1 Patients eligible for the AF cohort Patients that had a first prescription for apixaban during the identification period without previous prescriptions for NOACs or warfarin during the preceding 12 months Warfarin subcohort 1 Patients eligible for the AF cohort Patients that had a first prescription for warfarin during the identification period without previous prescriptions for NOACs or warfarin during the preceding 12 months Apixaban subcohort 2 Patients eligible for the AF cohort Patients that had a first prescription for apixaban during Exclusion Criteria: For the AF cohort: Patients with valvular AF will be excluded (see definition Appendix 1) Warfarin subcohort 1: Patients will be excluded from this sub-cohort if they had at least one prescription for warfarin or NOACs during the 12-month period preceding the first prescription for warfarin during the identification period, ie, the index date

Ages Eligible for Study
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Minimum Age: 18 Years

Sexes Eligible for Study
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All

Accepts Healthy Volunteers
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No

Study Plan
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How is the study designed?
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Arms and Interventions

| Participant Group/Arm | Intervention/Treatment |
| --- | --- |
| Patients for filled prescriptions for apixaban<br> | |
| Patients for filled prescriptions for warfarin<br> | |

What is the study measuring?
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Primary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Compare adherence among Atrial Fibrillation (AF) patients initiating treatment with apixaban (without previous warfarin or novel anticoagulant (NOAC) use) compared with those initiating treatment with warfarin (without previous warfarin or NOAC use) | Adherence: Adherence will be defined including missing doses and treatment discontinuation using the following approaches: Drug at disposal approach: Based on information on prescribed dosing (mg/day) and information on filled prescriptions (mg expensed from the pharmacy); it is possible to calculate for how long a period the drug will last for that specific patient. Adherence is then defined using the Medication Possession Ratio (MPR) calculated as the ratio of number of days of treatment supply divided by the total length of follow-up time, and converted to a percentage (in the graph below illustrated as the sum of the grey horizontal bars divided by the length of follow-up, ie, time between index date and end of follow-up). The MPR will be computed as a continuous and binary variable (MPR>80%, ie, high vs low adherence) | approximately 6 to 12 months | 
| Compare persistence among AF patients initiating treatment with apixaban (without previous warfarin or NOAC use) compared with those initiating treatment with warfarin (without previous warfarin or NOAC use) | Persistence: Persistence will be defined as treatment discontinuation and will be measured by estimating the following: Time to discontinuation: Date of therapy cessation is not possible to determine with certainty due to the nature of registry data. In order to be able to estimate the time of discontinuation, patients will be considered on treatment for the full time between two purchases as long as they have at least one refill in a six month period. If there is no new purchase within six months the patient is considered to have terminated treatment at a date corresponding to how long the last prescription will last (in the graph below illustrated as the time between index date and the end of the last horizontal bar). Cumulative incidence of persistent patients still on index treatment at the every 3- month interval after index date (treatment initiation) | approximately 6 to 12 months | 

Secondary Outcome Measures

| Outcome Measure | Measure Description | Time Frame |
| --- | --- | --- |
| Describe and compare patient characteristics (demographics) among AF patients through questionnaire | Describe and compare patient characteristics (eg, demographics and clinical) among AF patients who: Initiate apixaban without previous anticoagulant treatment (warfarin or NOAC use) Initiate apixaban with previous war Demographic parameters : Age-groups, Sex, Socioeconomic variables (e.g. education, disposable income) | approximately 6 to 12 months | 
| Describe and compare patient characteristics (clinical) among AF patients through questionnaire | Describe and compare patient characteristics (eg, demographics and clinical) among AF patients who: Initiate apixaban without previous anticoagulant treatment (warfarin or NOAC use) Initiate apixaban with previous war Clinical Characteristics: History of stroke/TIA/systemic, embolism, Diabetes, Hypertension, Heart failure, Vascular disease, Intracranial bleeding, Any bleeding, Kidney disease, Liver disease, Dementia, Valvular AF, Ischemic stroke, Unspecified stroke, TIA, Systemic embolism, Coronary disease, End Stage Renal Disease | approximately 6 to 12 months |