Limited English proficient patients and time spent in therapeutic range in a warfarin anticoagulation clinic

Abstract

Background: While anticoagulation clinics have been shown to deliver tailored, high-quality care to patients receiving warfarin therapy, communication barriers with limited English proficient (LEP) patients may lead to disparities in anticoagulation outcomes.

Methods and results: We analyzed data on 3770 patients receiving care from the Massachusetts General Hospital Anticoagulation Management Service (AMS) from 2009 to 2010. This included data on international normalized ratio (INR) tests and patient characteristics, including language and whether AMS used a surrogate for primary communication. We calculated percent time in therapeutic range (TTR for INR between 2.0 and 3.0) and time in danger range (TDR for INR <1.8 or >3.5) using the standard Rosendaal interpolation method. There were 241 LEP patients; LEP patients, compared with non-LEP patients, had a higher number of comorbidities (3.2 versus 2.9 comorbidities, P=0.004), were more frequently uninsured (17.0% versus 4.3%, P<0.001), and less educated (47.7% versus 6.0% ≤high school education, P<0.001). LEP patients compared with non-LEP patients spent less TTR (71.6% versus 74.0%, P=0.007) and more TDR (12.9% versus 11.3%, P=0.018). In adjusted analyses, LEP patients had lower TTR as compared with non-LEP patients (OR 1.5, 95% CI [1.1, 2.2]). LEP patients who used a communication surrogate spent less TTR and more TDR.

Conclusion: Even within a large anticoagulation clinic with a high average TTR, a small but significant decrease in TTR was observed for LEP patients compared with English speakers. Future studies are warranted to explore how the use of professional interpreters impact TTR for LEP patients.

Keywords: adverse drug events; limited English proficiency; outcomes research; quality of care; warfarin.