A 5-variable risk score (anemia, severe renal disease, age ≥75, prior bleeding, hypertension) predicted warfarin-associated major hemorrhage with a c-index of 0.74, outperforming 6 existing schemes.
Cohort (n=9,186)
Does a new 5-variable risk score accurately predict warfarin-associated hemorrhage in patients with atrial fibrillation compared to existing risk schemes?
A simple 5-variable risk score (anemia, severe renal disease, age ≥75, prior bleeding, hypertension) effectively quantifies the risk of major hemorrhage in atrial fibrillation patients on warfarin, outperforming existing schemes.
Effect estimate: c-index 0.74
OBJECTIVES: The purpose of this study was to develop a risk stratification score to predict warfarin-associated hemorrhage. BACKGROUND: Optimal decision making regarding warfarin use for atrial fibrillation requires estimation of hemorrhage risk. METHODS: We followed up 9,186 patients with atrial fibrillation contributing 32,888 person-years of follow-up on warfarin, obtaining data from clinical databases and validating hemorrhage events using medical record review. We used Cox regression models to develop a hemorrhage risk stratification score, selecting candidate variables using bootstrapping approaches. The final model was internally validated by split-sample testing and compared with 6 published hemorrhage risk schemes. RESULTS: We observed 461 first major hemorrhages during follow-up (1.4% annually). Five independent variables were included in the final model and weighted by regression coefficients: anemia (3 points), severe renal disease (e.g., glomerular filtration rate <30 ml/min or dialysis-dependent, 3 points), age ≥75 years (2 points), prior bleeding (1 point), and hypertension (1 point). Major hemorrhage rates ranged from 0.4% (0 points) to 17.3% per year (10 points). Collapsed into a 3-category risk score, major hemorrhage rates were 0.8% for low risk (0 to 3 points), 2.6% for intermediate risk (4 points), and 5.8% for high risk (5 to 10 points). The c-index for the continuous risk score was 0.74 and 0.69 for the 3-category score, higher than in the other risk schemes. There was net reclassification improvement versus all 6 comparators (from 27% to 56%). CONCLUSIONS: A simple 5-variable risk score was effective in quantifying the risk of warfarin-associated hemorrhage in a large community-based cohort of patients with atrial fibrillation.
“The majority of patients with atrial fibrillation – at least 70 percent -- would probably benefit from warfarin or other anticoagulation therapies. Based on our risk-stratification scoring, about 10 percent of patients who take warfarin are in the high bleeding-risk category. However, the majority of patients fall into the low bleeding-risk group.”
Fang et al. (Fri,) conducted a cohort in Atrial fibrillation (n=9,186). 5-variable risk score vs. 6 published hemorrhage risk schemes was evaluated on First major hemorrhage (c-index 0.74). A 5-variable risk score (anemia, severe renal disease, age ≥75, prior bleeding, hypertension) predicted warfarin-associated major hemorrhage with a c-index of 0.74, outperforming 6 existing schemes.