Anticoagulation control in the peri-hospitalization period

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 1 September 1999 and 1 September 2000 taking OACs. Results showed that 951 (17.7%) were hospitalized during their 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-hospitalization period. Anticoagulated patients discharged after medical hospitalizations could be targeted for improved anticoagulation control.