Oral anticoagulants (OAC) are effective and safe if the international normalized ratio (INR) is maintained within a narrow therapeutic range. Hospitalization is independently associated with poor anticoagulation control. The objective of this study is to describe how anticoagulation control changes in the peri-hospitalization period.
This study is a retrospective cohort study using population-based administrative databases. INR results were retrieved from a population-based laboratory database. INR levels between laboratory measures were estimated using linear interpolation. Auto-regressive, integrated, moving average (ARIMA) time-series modeling was used to determine how anticoagulation control changed in the peri-hospitalization period. The study included 5,380 elderly patients in Eastern Ontario between September 1, 1999 and September 1, 2000 taking OACs.
Results showed that 951 (17.7%) were hospitalized during the OAC therapy [thrombotic, n=52 (1.0%); hemorrhagic, n=140 (2.6%); other hospitalization types, n=759 (14.1%)]. All measures of anticoagulation control changed significantly in the peri-hospitalization period. Before hemorrhagic admissions, mean INR and proportion with INR >5 increased significantly (daily increase 0.024, P=.03 and 0.2%, P=.01). Following other hospitalization types, the proportion of patients with INR < 1.5 was significantly increased (daily increase 0.19%, P=.02).
Patients admitted to the hospital for a variety of indications have significantly worse anticoagulation control in the peri-hosptialization period. Anticoagulated patients discharged after medical hospitalizations could be targeted for improved anticoagulation control.