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| Racial discrepancies in warfarin use revealed |
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10 March 2006
US researchers have uncovered poor rates of warfarin prescription and International Normalized Ratio (INR) monitoring in Black and Hispanic atrial fibrillation patients compared with White patients. "Given the inconsistent monitoring and suboptimal use of warfarin therapy, there is a great need for anticoagulants that do not require monitoring," say Dr Elena Birman-Deych (Washington University School of Medicine, St Louis, Missouri) and colleagues.
Analysis of the records of 16,007 Medicare beneficiaries with atrial fibrillation who were hospitalised between 1998 and 1999 showed that just under half had received warfarin at discharge. This figure represented 64.6% of patients who had no contraindications for the drug. Further investigation revealed that although Black patients were more likely to have prior ischaemic stroke, there was a 31% reduction in the rate of warfarin prescription for these patients compared with Whites, while Hispanics were given the drug half as often as White patients. Furthermore, 21.3% and 16.7% of Black and Hispanic recipients of warfarin, respectively, were lost to INR monitoring, compared with 9.7% of White patients, and Black and Hispanic patients were monitored less frequently than White patients.
"The effectiveness of warfarin was also disappointing," the team writes in the journal Stroke. The use of warfarin in White patients was associated with a 41% reduction in the rate of stroke, compared with the 65% reduction reported in clinical trials. The authors stated: "The results were even more discouraging in Black and Hispanic Medicare beneficiaries, for whom there was no evidence that warfarin prevented strokes." They speculate that the higher burden of diabetes and hypertension reported in these populations may lead to an increased incidence of non-cardioembolic strokes, against which warfarin is less effective than against other stroke subtypes.
The researchers suggest that the lower frequency of INR monitoring in Blacks and Hispanics may have contributed to the higher stroke rates, although they were unable to determine whether this was due to poor access to services, or to lack of patient compliance. In conclusion, the team stresses: "Because confounding and poor monitoring may be responsible for the apparent poor protection against stroke, especially in minority populations, our findings should not be used to justify withholding therapy to any population."
Reference:
Stroke 2006; 37 (4): 1070-1074.
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