Study casts doubt on D-dimer test to exclude PE in COVID patients

2020 03 03 21 27 5948 Blood Clot 400

A retrospective diagnostic study evaluating the practice of using D-dimer assays to exclude pulmonary embolism (PE) among hospitalized COVID-19 patients showed that the test had limited clinical utility. The findings were published on October 8 in JAMA Network Open.

The motivation for the study was the fact that the study population used to originally validate the the D-dimer assay for excluding PE is different from the current population of hospitalized COVID-19 patients who face increased thrombotic risk and a higher pretest probability of PE.

The researchers, led by Dr. Constantine Logothetis of the University of South Florida in Tampa, evaluated different D-dimer thresholds, including fixed and age-adjusted thresholds, ranging from 0.5 µg/mL to 20 µg/mL. They compared the D-dimer tests with the computed tomography pulmonary angiography (CTPA) standard.

A D-dimer concentration of 0.05 µg/mL was associated with a sensitivity of 100% and specificity of 8.8%. The age-adjusted threshold was associated with a sensitivity of 94.6% and specificity of 22.8%.

Among 287 patients with COVID-19 and suspected PE, 118 patients required intensive care unit levels of care, and 27 patients died during hospitalization.

Of the 287 patients, 37 had radiographic evidence of PE and 250 did not; 265 had plasma D-dimer levels of 0.05 µg/mL or more (92.3%), including all patients with PE and 225 of 250 patients without PE (91.2%).

"If using D-dimer to exclude patients with PE, the increased values we found among 92.3% of patients suggest that this assay would be less useful than in the populations in which it was originally validated, among which a minority of patients had increased D-dimer values," the authors wrote.

Setting the D-dimer thresholds higher improved specificity but also increased the false-negative rate to a level that could present an "unacceptable patient safety risk," Logothetis and colleagues noted.

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