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11-10-2010 | Cardiology | Article

Predictors of poor INR control revealed


Free abstract

MedWire News: Research shows that factors including repeat hospitalizations, multiple drug prescriptions, and alcohol abuse adversely impact on the time patients receiving warfarin spend within a therapeutic International Normalized Ratio (INR) range.

The findings can be used to "identify patients who may require greater attention or innovative management strategies to achieve acceptable levels of anticoagulation control," say Adam Rose (Bedford VA Medical Center, Massachusetts, USA) and co-workers.

The researchers found that predictors of time spent within a therapeutic INR range (TTR) varied between the first 6 months of warfarin therapy (inception period; 39,447 patients) and the period thereafter (104,505 patients).

Patients' average TTR was lower during inception than during long-term treatment, at 48% versus 61%, they report in the Journal of Thrombosis and Haemostasis.

The most important predictor of a lower TTR during both periods was repeat hospitalization, with two or more hospitalizations reducing the TTR during inception by 7.3%, and four or more reducing it by 9.4% during long-term treatment, relative to no hospitalizations.

The researchers note that the negative impact of hospitalization on warfarin management has now been demonstrated in multiple studies, and stress that hospitalized patients should receive "prompt and vigilant follow-up after discharge" to ensure continued good anticoagulation management.

Patients taking 16 or more medications had a TTR that was 4.3% lower than that of patients taking 0-7 medications during the inception period and 5.1% lower during the long-term period. Alcohol abuse reduced TTR by 4.6% during inception and 5.4% in the long term.

During inception, having cancer or bipolar disorder reduced patients' TTRs, while other negative predictors in the long-term were female gender, cancer, dementia, substance abuse, and chronic liver disease.

"The effect of each individual variable upon TTR in our study was relatively small, and no single risk factor that we studied establishes a patient as being too high-risk for anticoagulation therapy to be contemplated," the researchers stress.

"In combination, however, the variables that we studied would indeed be useful for risk-stratifying patients receiving oral anticoagulation."

The team therefore created a clinical prediction tool based on these variables, which is available online.

MedWire ( is an independent clinical news service provided by Current Medicine Group, a trading division of Springer Healthcare Limited. © Springer Healthcare Ltd; 2010

By Eleanor McDermid


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