Age-Adjusted Cutoff D-Dimer Level to Rule Out Acute Pulmonary Embolism: A Validation Cohort Study

Abstract

BackgroundThe diagnosis of pulmonary embolism in the Emergency Room setting is challenging. Multiple patients have to undergo radiologic assessment with its inherent shortcomings. The D-dimer test with accepted cutoff level of 500 μg/L is associated with a high proportion of false-positive results. The present study aimed to validate the advantages of using an age-adjusted D-dimer cutoff level, compared with 500-μg/L value in the diagnosis of acute pulmonary embolism. MethodsThis study evaluated patients admitted to the Rambam Emergency Room between 2011 and 2014 with a suspected diagnosis of pulmonary embolism. Patient data, D-dimer plasma levels, and imaging results were collected. The study cohort was subdivided according to the D-dimer levels below and above 500 μg/L. The group with levels above 500 μg/L was further assessed using the newly suggested age-adjusted D-dimer cutoff level, defined as age multiplied by 10. ResultsFiles of 1241 patients were reviewed; 654 patients with low or intermediate risk for pulmonary embolism had a D-dimer level above 500 μg/L. Two hundred eight (208) patients had a D-dimer level above 500 μg/L but below the age-adjusted cutoff value; one of them was diagnosed with pulmonary embolism (0.48% [95% confidence interval 0%-2.6%]). Four hundred forty-six (446) patients had a D-dimer level above the age-adjusted cutoff value, and 28 of them were diagnosed with pulmonary embolism (6.28% [95% confidence interval 4.2%-8.9%]), representing a negative predictive value of 99.5% for the age-adjusted cutoff level. ConclusionsAn age-adjusted D-dimer cutoff level may be safely used to exclude pulmonary embolism in patients with a low or intermediate probability for acute pulmonary embolism, alleviating the need to perform unnecessary imaging evaluations.