Warfarin Patients With Anemia Show Trend of Out-of-Range International Normalized Ratio Frequency With Point-of-Care Testing in an Anticoagulation Clinic

Abstract

Introduction: Many factors influence international normalized ratio (INR); however, few studies have examined the impact of anemia in warfarin patients. The primary objective of this study was to explore the relationship between in-clinic anemia and the control of INR within an anticoagulation clinic. Methods: A retrospective chart review was performed on a random sample of patients seen in an academic medical center pharmacy-managed anticoagulation clinic. Hemochron® Signature Elite machine was utilized to monitor point-of-care (POC) INR. In-clinic anemia was defined as hematocrit <32%. Statistical analyses were conducted using STATA MP a webbased platform (https://www.stata.com/statamp/). Results: Of the 300 patients analyzed, 45 (15%) patients had in-clinic anemia. Patients with in-clinic anemia were more likely to be younger (P < .05), female (P < .05), and have a diagnosis of sickle cell disease or anemia (P < .05). In the unadjusted logistic regression model, patients with in-clinic anemia were less likely to have an in-range INR ( OR: 0.52; 95% CI: 0.27-0.98). The adjusted regression model did not show significance. Conclusion: Study results suggest that in-clinic anemia may be more prevalent among younger, female patients prescribed warfarin, and patients diagnosed with in-clinic anemia may be a risk factor for out-of-range INR. Pharmacists practicing in anticoagulation clinics can incorporate this information into patient care practice in efforts to maintain optimal management.