Elevated D-Dimer Values Can Help Select Better COVID-19 Patients for CT Pulmonary Angiography

December 3, 2020
Whitney J. Palmer

Whether a patient has a pulmonary embolism, a higher-than-normal D-dimer value can help identify patients for whom CTPA is most appropriate, alleviating some workload from emergency radiology.

D-dimer values can help providers determine which COVID-19-positive patients should undergo CT pulmonary angiography (CTPA) to rule out the presence of a pulmonary embolism (PE), potentially alleviating some of the current workload for emergency radiology.

In research presented during this year’s Radiological Society of North America (RSNA) annual meeting, investigators from the Hospital Universitario Ramón y Cajal in Madrid, share that there is a statistically significant difference in D-dimer levels between COVID-19-positive patients who have a PE and those who do not. Including those values in decision-making around imaging could reduce the number of patients sent for scanning, the team said.

“As a consequence of the inconclusive clinical and analytical criteria, selection of COVID-19 patients for CTPA may be a daunting task,” they said. “This has resulted in a noticeable increase in CTPA requests in the emergency radiology setting and has led us to ask ourselves if a better CTPA selection of COVID-19 patients is possible.”

PE is one of the more common complications that occurs in COVID-19-positive patients, and knowing whether a patient is PE-positive can potentially help providers avoid a fatality. Based on the results of their analysis, the team said, D-dimer values could be useful in pre-test probability assessments of PE in COVID-19 positive patients.

To make this determination, they evaluated CTPA scans from 187 COVID-19 positive patients – 119 men and 68 women – imaged in their institution this year from March 1 to April 20. The scan was performed with a 320-detection CT scanner after a 5 mL/s contrast agent injection. The team assessed both the D-dimer rate within 48 hours of the CTPA, as well as whether a PE were present, what the PE characteristics were, such as lateral, unilateral, or bilateral, and the area affected.

Among the group, 59 patients were PE-positive, and 128 were PE-negative. The most frequently affected lobe was the right lower lobe, and the most proximal affected branch was on the segmental level. Based on their evaluation, the median D-dimer values for PE-positive and PE-negative patients were 9,668 ng/mL and 2,233 ng/mL, respectively, revealing a statistically significant difference (p<0.01), the team said.

“This might allow a better management of CTPA requests in COVID-19 patients,” they said, “and, thus, help relieve the burden on emergency radiology departments.”

Still, they said, special attention to be paid to the value that is actually used to determine who is sent for CTPA scanning. Among COVID-19 positive patients, the cut off value for PE probability prediction should be higher than what is used in non-COVID-19 positive patients because the D-dimer values in patients who have the virus are typically above what is considered normal for both PE-positive and PE-negative groups anyway.

To identify an acceptable and accurate value, the team suggested, further research is needed.

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