Dear Editor,

We read with interest Mohammed et al's excellent review regarding clinical presentation and risk stratification of pulmonary embolism (PE) that was recently published in the Journal.[1]

We have, however, concerns about the authors' strategy about the use of D-dimer testing to select which low- and intermediate-risk patients with suspected PE should proceed to imaging. Mohammed et al advocate the use of a single D-dimer cutoff level (500 ng/mL) to help make this decision. However, in recent years, it has been increasingly recognized that D-dimer cutoff levels, adjusted to such clinical factors as age and pretest clinical probability, improve the accuracy of diagnosis of PE.[2] [3] D-dimer levels increase with age and, thus, use of a rigid, fixed D-dimer cutoff level of 500 ng/mL results in a considerable decrease in specificity in older patients. Righini et al suggested adapting D-dimer cutoff levels to the patient's age to overcome this problem.[2] In the Age-Adjusted D-Dimer Cutoff Levels to Rule Out Pulmonary Embolism trial, for patients ≤50 years, the D-dimer threshold of 500 ng/mL was used. For patients >50 years, the D-dimer cutoff level was calculated as age multiplied by 10 ng/mL. This strategy resulted in a very low rate of missed diagnoses of PE (in only 0.3% of patients). In addition, it was estimated that the use of these age-adjusted D-dimer thresholds resulted in a >20% absolute reduction in imaging studies.[2]

In the Diagnosis of Pulmonary Embolism with D-Dimer Adjusted to Clinical Probability study, an algorithm combining clinical pretest probability and varying D-dimer levels was found to be very useful.[3] A combination of low clinical pretest probability (using the Wells score[4]) and a D-dimer level less than 1,000 ng/mL accurately identified patients at low risk for PE at follow-up and these patients were excluded from chest imaging. This algorithm was associated with a remarkably low (0.05%) rate of missed diagnoses of venous thromboembolism and an absolute reduction of chest imaging of 18%.

We would urge all clinicians involved in the diagnosis and care of patients with suspected PE to be aware of the above studies.

Article published online:
01 October 2024

© 2024. International College of Angiology. This article is published by Thieme.

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