Background

The use of warfarin in older patients requires special consideration because of concerns with comorbidities, interacting medications, and the risk of bleeding. Several studies have suggested that warfarin may be underused or inconsistently prescribed in long-term care (LTC); no published systematic review has evaluated warfarin use for stroke prevention in this setting. This review was conducted to summarize the body of published original research regarding the use of warfarin in the LTC population.

Methods

A systematic literature search of the PubMed, Cumulative Index to Nursing and Allied Health Literature, and Cochrane Library was conducted from January 1985 to August 2010 to identify studies that reported warfarin use in LTC. Studies were grouped by (1) rates of warfarin use and prescribing patterns, (2) association of resident and institutional characteristics with warfarin prescribing, (3) prescriber attitudes and concerns about warfarin use, (4) warfarin management and monitoring, and (5) warfarin-related adverse events. Summaries of study findings and quality assessments of each study were developed.

Results

Twenty-two studies met the inclusion criteria for this review. Atrial fibrillation (AF) was the most common indication for warfarin use in LTC and use of warfarin for stroke survivors was common. Rates of warfarin use in AF were low in 5 studies, ranging from 17% to 57%. These usage rates were low even among residents with high stroke risk and low bleeding risk. Scored bleeding risk had no apparent association with warfarin use in AF. In physician surveys, factors associated with not prescribing warfarin included risk of falls, dementia, short life expectancy, and history of bleeding. International normalized ratio was in the target range approximately half of the time. The combined overall rate of warfarin-related adverse events and potential events was 25.5 per 100 resident months on warfarin therapy.

Conclusions

Among residents with AF, use of warfarin and maintenance of INR levels to prevent stroke appear to be suboptimal. Among prescribers, perceived challenges associated with warfarin therapy often outweigh its benefits. Further research is needed to explicitly consider the appropriate balancing of risks and benefits in this frail patient population.

OBJECTIVE

To evaluate laboratory safety monitoring in patients taking selected chronic prescription drugs.

DESIGN

Retrospective study using 1999–2001 claims data to calculate rates of missed laboratory tests (potential laboratory monitoring errors). Eleven drugs/drug groups and 64 laboratory tests were evaluated.

SETTING

Two staff/network model health maintenance organizations.

PATIENTS

Continuously enrolled health plan members age≥19 years taking ≥1 chronic medications.

MEASUREMENTS AND MAIN RESULTS

Among patients taking chronic medications (N=29,823 in 1999, N=32,423 in 2000, and N=36,811 in 2001), 47.1% in 1999, 45.0% in 2000, and 44.0% in 2001 did not receive ≥1 test recommended for safety monitoring. Taking into account that patients were sometimes missing more than 1 test for a given drug and that patients were frequently taking multiple drugs, the rate of all potential laboratory monitoring errors was 849/1,000 patients/year in 1999, 810/1,000 patients/year in 2000, and 797/1,000 patients/year in 2001. Rates of potential laboratory monitoring errors varied considerably across individual drugs and laboratory tests.

CONCLUSIONS

Lapses in laboratory monitoring of patients taking selected chronic medications were common. Further research is needed to determine whether, and to what extent, this failure to monitor patients is associated with adverse clinical outcomes.