D-dimer useful in ruling out pulmonary embolisms in hospitalized COVID-19 patients

Oct. 28, 2021

Researchers at the University of South Florida Health (USF Health) Morsani College of Medicine reported that a screening blood test originally validated in seriously ill patients without COVID-19 is still clinically useful for ruling out pulmonary embolism in patients hospitalized with the coronavirus, according to a news release from USF Health.

Doctors who suspect pulmonary embolisms routinely rely on widely available D-dimer screening to rule out pulmonary embolisms, as the test measures protein fragments of blood clots in the bloodstream. The normally nearly low levels of D-dimer tend to rise sharply as the body breaks down clots. Principal Investigator Asa Oxner, MD, and USF Health colleagues published a single-center, diagnostic study Oct. 8 in JAMA Network Open investigating how well D-dimer testing performed at excluding pulmonary embolism in patients hospitalized with COVID-19.

Pulmonary embolisms occur when blood clots that form in another part of the body (often the leg), travel through the bloodstream, and lodge in the blood vessels of the lung, decreasing blood flow and causing low oxygen levels.

Research indicates COVID-19 patients are three to 10 times more likely to develop pulmonary embolisms than other hospitalized patients, even when they are not as seriously ill or immobilized,  , Oxner said. Scientists are still investigating why, but it appears the COVID-19 virus may create a cellular environment that promotes clotting by making the inside of blood vessels uneven, irritated, and prone to microtears.

The researchers also analyzed whether changing the cutoff levels defining positive or negative D-dimer test results specifically for the COVID patient population might improve the test’s performance. “We did not find that to be statistically significant; however, we may have been able to identify a different cutoff level if the study had more COVID patients,” Oxner said.

Within the limitations of this single-center study, setting higher D-dimer thresholds was associated with improved specificity — but at “the cost of an increased false-negative rate that could be associated with an unacceptable patient safety risk,” the study authors wrote. A false-negative result means that the test does not detect a pulmonary embolism when the serious blood clotting problem is very likely present.

While clinicians must maintain heightened suspicion for pulmonary embolisms when evaluating symptoms in COVID-19 patients, the overall USF Health study results indicate that the currently available D-dimer test adequately screens for the likelihood of pulmonary embolism in hospitalized COVID patients, Oxner said. 

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