Factors Affecting Prothrombin Time Normalization After Stopping Warfarin
Author Information
Author(s): Sam Schulman, Rajae Elbazi, Michelle Zondag, Martin O'Donnell
Primary Institution: McMaster University
Hypothesis
What clinical characteristics influence the normalization of prothrombin time after stopping warfarin before surgery?
Conclusion
Baseline INR is associated with the rate of normalization of prothrombin time after stopping warfarin, but it is not a reliable predictor in clinical practice.
Supporting Evidence
- 7% of patients did not normalize their prothrombin time after stopping warfarin for 5 days.
- Baseline INR was the only significant predictor of slow normalization of prothrombin time.
- Patients with a baseline INR of 3.0 or higher had a low positive predictive value for slow normalization.
Takeaway
When patients stop taking warfarin before surgery, their blood's ability to clot can take time to return to normal, and this study found that the initial INR level is important for predicting how long it will take.
Methodology
Retrospective cohort study analyzing clinical data from patients who stopped warfarin before surgery.
Potential Biases
Potential selection bias due to exclusion of patients without INR values on the day of surgery.
Limitations
The study did not analyze genetic factors affecting warfarin metabolism and may have selection bias.
Participant Demographics
Patients included were anticoagulated with warfarin for at least one month, with a mean age of 69.4 years.
Statistical Information
P-Value
0.003
Confidence Interval
0.12–0.62
Statistical Significance
p<0.05
Digital Object Identifier (DOI)
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