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It’s Time to Use an Age-based Approach to D-dimer

An age-adjusted <font size="2">D</font>-dimer cutoff—rather than the conventional 500 μg/L value—is a better way to rule out VTE in patients older than 50.

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PRACTICE CHANGER

Use an age-adjusted d-dimer cutoff (patient age in years × 10 μg/L) for patients older than 50 when evaluating for venous thromboembolism (VTE); it reduces false-positives without substantially increasing false-negatives.1

STRENGTH OF RECOMMENDATION

A: Based on consistent and good-quality patient-centered evidence from a meta-analysis of cohort studies.1

ILLUSTRATIVE CASE

A 78-year-old woman with no significant medical history or recent immobility comes to your clinic complaining of left lower extremity pain and swelling. Her d-dimer is 650 μg/L. What is your next step?

Although d-dimer is recognized as a reasonable screening tool for VTE, the specificity of d-dimer testing using a conventional cutoff value of 500 μg/L is particularly poor in patients older than 50. In low-risk patients older than 80, the specificity is 14.7%.2-5 As a result, conventional d-dimer testing is not very helpful for ruling out VTE in older patients.2-5

Improved testing is needed for a population at heightened risk

In the United States, there are more than 600,000 cases of deep vein thrombosis (DVT) and pulmonary embolism (PE) each year.2 The incidence of PE increases from 1:1,000 in younger patients to 8:1,000 in older patients,4 and the mortality rate can reach 30%.6 The gold standards of venography and pulmonary angiography have been replaced by less burdensome tests, primarily lower extremity duplex ultrasound and CT pulmonary angiogram. However, even these tests are expensive and often present logistical challenges in elderly patients. For these reasons, it is helpful to have a simple, less-expensive tool to rule out VTE in older patients who have signs or symptoms.

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