Background: Observations by pharmacists monitoring anticoagulated patients suggested that patients with diabetes often require more frequent international normalized ratio (INR) monitoring than patients without diabetes. The purpose of this investigation was to examine the association between glycemic control and therapeutic anticoagulation control.
Methods: Patients with diabetes who were receiving warfarin therapy monitored by the Kaiser Permanente of Colorado Clinical Pharmacy Anticoagulation Service were eligible for inclusion. Patients were included if they had a diagnosis of diabetes mellitus type 1 or 2, aged > or =18 years, and had initiated anticoagulant therapy > or =120 days before their most recent hemoglobin A1C measurement. The primary outcome was the correlation between hemoglobin A1C value and percent of time in the patient-specific INR range. Multivariate analysis was undertaken to regress percent of time in INR range on an A1C value > or =8.0 while adjusting for other possible explanatory variables.
Results: A total of 911 patients with diabetes were included in the study. Subjects with an A1C value > or =8.0 had similar characteristics as those subjects with an A1C value < 8.0. Correlation analysis revealed no relationship between percent of time spent in INR range and A1C value (Spearman Correlation Coefficient = 0.012, p = 0.805). Multivariate analysis revealed no relationship between percent of time spent in INR range and A1C value > or =8.0 (Odds Ratio = 1.00; 95% Confidence Interval = 0.99, 1.01) when adjusting for possible explanatory variables.
Conclusions: For patients with diabetes on warfarin anticoagulation therapy, there is no association between glycemic control and therapeutic anticoagulation control. However, anticoagulation therapy providers should manage these patients with the same diligence and care as patients without diabetes.