Key result
One quarter of patients failed to reach INR stabilization; those who achieved it within 1 year were 10 times more likely to remain on warfarin than those who did not.
Why the study?
What factors predict INR stabilization and long-term utilization in newly initiated warfarin patients with nonvalvular atrial fibrillation?
Observational (n=15,276)
Yes
What factors predict INR stabilization and long-term utilization in newly initiated warfarin patients with nonvalvular atrial fibrillation?
Effect estimate: 10 times more likely
A significant proportion of NVAF patients newly initiated on warfarin fail to achieve INR stabilization, which strongly predicts long-term discontinuation of the therapy.
INR non-stabilization flags high discontinuation risk in new warfarin users; hypothesis-generating for adherence interventions in NVAF.
BACKGROUND: Warfarin is effective for stroke prevention in patients with atrial fibrillation (AF), but international normalized ratio (INR) levels fluctuate and frequent monitoring is necessary. METHODS: This study used data from a large anticoagulation management service database to analyze the relationship between INR stabilization and warfarin utilization for >1 year in patients with nonvalvular AF (NVAF). Anticoagulation records from a large US electronic database collected from 2006 to 2010 were analyzed. RESULTS: Patients with NVAF and ≥ 3 INR values in the dataset were identified (n = 15,276). INR stabilization was defined as the first three consecutive INR values between 2.0 and 3.0 after warfarin initiation. One quarter of patients (n = 3809) failed to reach INR stabilization. After initial stabilization, 30% of subsequent INR values were out of range. The mean (± standard deviation [SD]) follow-up time from stabilization to the end of study for these patients was 494.2 ± 418.1 days. Age ≥ 75 years (odds ratio [OR] = 1.17, 95% confidence interval [CI] = 1.08-1.27), hypertension (OR = 1.19, 95% CI = 1.10-1.29), or prior stroke (OR = 1.29, 95% CI = 1.04-1.61) were positively associated with achieving stabilization; heart failure was negatively associated with stabilization (OR = 0.78, 95% CI = 0.70-0.87). Male gender (p < 0.0001) and hypertension were associated with earlier stabilization (p = 0.0013); heart failure was associated with later stabilization (p = 0.0098). Patients who achieved INR stabilization within 1 year were 10 times more likely to remain on warfarin than patients who did not achieve it. LIMITATIONS: Observational data may contain incomplete records. Data on adherence, concurrent medications, vitamin K intake, genotype, reasons for discontinuation of monitoring, and patient outcomes were not available in the dataset. The study findings were generalizable only to patients with AF who were managed by anticoagulation clinics. CONCLUSION: Given the importance of stroke prevention among patients with AF, the potential for unpredictable INR patterns should be carefully considered during clinical decision-making.
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Nelson et al. (2014) conducted an observational in nonvalvular atrial fibrillation (n=15,276). INR stabilization within 1 year vs. Failure to achieve INR stabilization within 1 year was evaluated on Remaining on warfarin (10 times more likely). One quarter of patients failed to reach INR stabilization; those who achieved it within 1 year were 10 times more likely to remain on warfarin than those who did not.
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