Lack of Daily Warfarin Monitoring in Hospitals Linked to Higher Risk of Adverse Events: AHRQ Study

Patients taking the anticoagulant warfarin while hospitalized for pneumonia, heart failure or heart attack or following major surgery are at increased risk of an adverse event if their body’s ability to clot blood is not tested daily, an AHRQ-funded research team found. Warfarin is a commonly used anticoagulant and is among medications often associated with adverse drug events. Patients who have high levels of international normalized ratios (INR), a measure of the blood’s ability to clot, are at higher risk for adverse events. To test the relationship between daily and less frequent INR monitoring and warfarin-associated adverse events, researchers analyzed data between 2009 and 2013 from the Medicare Patient Safety Monitoring System, a national chart abstraction system. Patients whose INR was not measured on two or more consecutive days had higher risks for warfarin-associated adverse events, particularly cardiac and surgical patients. A one-day increase in INR of more than 0.9 predicted a greater risk for overly high levels of the anticoagulant, researchers found. An abstract and the article, “Predictors of Warfarin-Associated Adverse Events in Hospitalized Patients: Opportunities to Prevent Patient Harm,” were published online in the December 14 issue of the Journal of Hospital Medicine.

2015 Dec 14. doi: 10.1002/jhm.2528. [Epub ahead of print]

Predictors of warfarin-associated adverse events in hospitalized patients: Opportunities to prevent patient harm.

Metersky ML1,2, Eldridge N3, Wang Y4, Jaser L1,5, Bona R6, Eckenrode S1, Bakullari A1, Andrawis M7, Classen D8, Krumholz HM9,10,11,12.

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Abstract

BACKGROUND:

The optimum international normalized ratio (INR) monitoring frequency for hospitalized patients receiving warfarin is unknown.

OBJECTIVE:

Assess relationship between daily versus less frequent INR monitoring and overanticoagulation and warfarin-related adverse events.

DESIGN:

Retrospective cohort study using Medicare Patient Safety Monitoring System data.

SETTING:

Randomly selected acute care hospitals across the United States.

PATIENTS:

Patients hospitalized from 2009 to 2013 for pneumonia, acute cardiac disease, or surgery who received warfarin.

INTERVENTIONS:

None.

MEASUREMENTS:

(1) Association between frequency of INR monitoring and an INR ≥6.0 or warfarin-related adverse event. (2) Association between the rate of change of the INR and a subsequent INR ≥5.0 and ≥6.0.

RESULTS:

Among 8529 patients who received warfarin for ≥3 days, for 1549 (18.2%) the INR was not measured on 2 or more days. These patientshad higher propensity-adjusted odds ratios (ORs) of having a warfarin-associated adverse event (OR: 1.48, 95% confidence interval [CI]: 1.02-2.17) for cardiac patients and surgical patients (OR: 1.73, 95% CI: 1.20-2.48), with no significant association for pneumonia patients. Cardiac and pneumonia patients with 1 day or more without an INR measurement had higher propensity-adjusted ORs of having an INR ≥6.0 (OR: 1.61, 95% CI: 1.07-2.41 and OR: 1.92, 95% CI: 1.36-2.71, respectively). A 1-day increase in the INR of ≥0.9 occurred in 621 patients (12.5%) and predicted a subsequent INR of ≥6.0 (positive likelihood ratio of 4.2).

CONCLUSION:

Daily INR measurement and recognition of a rapidly rising INR might decrease the frequency of warfarin-associated adverse eventsin hospitalized patients. Journal of Hospital Medicine 2015. © 2015 Society of Hospital Medicine.