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. 2007 Jun;22(6):727-35.
doi: 10.1007/s11606-006-0064-5. Epub 2007 Mar 31.

Anticoagulation control in the peri-hospitalization period

Carl van Walraven  1 , Alan J Forster
Affiliations

Anticoagulation control in the peri-hospitalization period

Carl van Walraven et al. J Gen Intern Med. 2007 Jun.

Abstract

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.

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Figures

Figure 1
Figure 1
Effect of hospitalization on daily mean INR. These plots present time series for daily mean INRs in four groups. In both plots, days from hospitalization is plotted on the horizontal axis and the mean INR is plotted on the vertical axis. Patients admitted with a thrombotic (blue line) or a hemorrhagic (red line) event are presented on the top plot; patients admitted with another hospitalization (purple line) are presented on the bottom plot. Patients who were not hospitalized act as the control group in both plots (black line). Error bars on each line are 83% confidence intervals; lines whose 83% confidence intervals do not touch are significantly different at that point with an α-error of 0.05.
Figure 2
Figure 2
Effect of hospitalization on daily proportion with critically low INR. These plots present time series for daily proportion of patients with an INR less than 1.5 in four groups. In both plots, days from hospitalization is plotted on the horizontal axis and the proportion of patients with an INR less than 1.5 is plotted on the vertical axis. Patients admitted with a thrombotic (blue line) or a hemorrhagic (red line) event are presented on the top plot; patients admitted with another hospitalization (purple line) are presented on the bottom plot. Patients who were not hospitalized act as the control group in both plots (black line). Error bars on each line are 83% confidence intervals; lines whose 83% confidence intervals do not touch are significantly different at that point with an α-error of 0.05.
Figure 3
Figure 3
Effect of hospitalization on daily proportion with critically high INR. These plots present time series for daily proportion of patients with an INR greater than or equal to 5.0 in four groups. In both plots, days from hospitalization is plotted on the horizontal axis and the proportion of patients with an INR ≥ 5.0 is plotted on the vertical axis. Patients admitted with a thrombotic (blue line) or a hemorrhagic (red line) event are presented on the top plot; patients admitted with another hospitalization (purple line) are presented on the bottom plot. Patients who were not hospitalized act as the control group in both plots (black line). Error bars on each line are 83% confidence intervals; lines whose 83% confidence intervals do not touch are significantly different at that point with an α-error of 0.05.
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