What question did this study set out to answer?

To quantify the absolute risk of thromboembolism associated with a significantly subtherapeutic international normalized ratio in patients with previously stable warfarin anticoagulation.

July 25, 2008Pharmacotherapy The Journal of Human Pharmacology and Drug Therapy

Thromboembolic Consequences of Subtherapeutic Anticoagulation in Patients Stabilized on Warfarin Therapy: The Low INR Study

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Why the study?

Does a subtherapeutic INR increase the risk of anticoagulation-related thromboembolism in adult patients stabilized on warfarin therapy?

Population

2,597 adult patients receiving warfarin with previously stable anticoagulation

Comparison

Subtherapeutic INR vs Maintained therapeutic INR

Design

Cohort

Follow-up

90 days

Authors

NCNathan P. ClarkKaiser Permanente DWDaniel M. WittPreventive Cardiology TDThomas DelateKaiser Permanente

Discussion

Member takes

Implication

Isolated subtherapeutic INR was associated with low thromboembolic risk; leaves open whether bridging is needed in stabilized warfarin patients.

Key Points

To quantify the absolute risk of thromboembolism associated with a significantly subtherapeutic international normalized ratio in patients with previously stable warfarin anticoagulation.
Retrospective matched cohort study of 2597 adult patients receiving warfarin within a centralized anticoagulation service between January 1998 and December 2005.
Patients with a low INR (≥0.5 units below therapeutic range; n=1080) were matched by index date, indication, and age to controls maintaining therapeutic INR (n=1517) across 90 days of follow-up.
Anticoagulation-related thromboembolism occurred in 4 patients (0.4%) in the low INR cohort compared with 1 patient (0.1%) in the therapeutic INR cohort (p=0.214).
No statistically significant differences occurred between cohorts in the overall rates or hazards of thromboembolism, bleeding, or death during the 90-day follow-up (p>0.05).

Structured PICO

Does a subtherapeutic INR increase the risk of anticoagulation-related thromboembolism in adult patients stabilized on warfarin therapy?

Population

2,597 adult patients receiving warfarin with previously stable anticoagulation (defined as two INR values measured at least 2 weeks apart within or above therapeutic range)

Intervention

Subtherapeutic INR (third INR value ≥0.5 units below therapeutic range)

Comparator

Maintained therapeutic INR (third therapeutic INR value and no INR value ≥0.2 units below target in ensuing 90 days)

Outcome

Anticoagulation-related thromboembolism during the 90 days after the index INRhard clinical

Patients stabilized on warfarin who experience a significant subtherapeutic INR have a low risk of thromboembolism at 90 days, suggesting anticoagulant bridge therapy may not be necessary for isolated subtherapeutic periods.

Cite This Study

Clark et al. (2008) studied this question.

synapsesocial.com/papers/6a71560735aa2c282ce2a532 https://doi.org/10.1592/phco.28.8.960

Topics

Anticoagulation in AF

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Implication

Isolated subtherapeutic INR was associated with low thromboembolic risk; leaves open whether bridging is needed in stabilized warfarin patients.

Thromboembolic Consequences of Subtherapeutic Anticoagulation in Patients Stabilized on Warfarin Therapy: The Low INR Study

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Topics

Thromboembolic Consequences of Subtherapeutic Anticoagulation in Patients Stabilized on Warfarin Therapy: The Low INR Study

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Also Consider

Topics

Also Consider