Better way to interpret blood tests to diagnose pulmonary embolism

November 27, 2019

HAMILTON, ON (November 27, 2019) - A study led by Hamilton researchers has found a new way to interpret blood test results in patients who are investigated for blood clots in their lungs, a condition known as pulmonary embolism.

This new approach applies to D-dimer blood tests, which are used by physicians to rule out the presence of a blood clot. Researchers found that a higher than usual D-dimer level can be considered a negative result if the physician has assessed the patient as having a low probability of having a pulmonary embolism.

The study team notes the findings are important as they mean a lot fewer patients need a computerized tomography (CT) scan, which results in patients avoiding radiation exposure and spending less time in the emergency department. The health system also benefits, they say, as it frees up CT scans for other patients and it improves ability to move patients more quickly through the emergency department.

The study results were published today in the New England Journal of Medicine.

"The primary goal of diagnostic testing for pulmonary embolism is to identify which patients should be treated with anticoagulant agents and which should not," said first author Clive Kearon, professor of medicine at McMaster University and a thrombosis specialist with Hamilton Health Sciences.

"When a physician is concerned that pulmonary embolism may be present, chest imaging with CT pulmonary angiography is usually done in half of these patients. We wanted to find a way to reduce the number of CT scans that need to be done."

A total of 2,017 patients aged 18 and older were enrolled and evaluated in the study, of which seven per cent had pulmonary embolism on initial diagnostic testing. The average age of the patients was 52 years, and 66 per cent were female.

Of the patients in the study, 73 per cent, or 1,474, were enrolled at Hamilton Health Sciences or St. Joseph's Healthcare Hamilton.

These patients, and those at other university-based clinical centres in Canada, were tested from December 2015 through May 2018 and assessed 90 days later.

Of the 1,325 patients identified by an emergency department physician as having a low (1,285 of the patients) or a moderate (40 patients) probability of having a pulmonary embolism and who had negative D-dimer results (that is, less than 1,000 or 500 nanograms per millilitre (ng/mL) respectively), none had venous thromboembolism during follow-up.

"Our analyses show that pulmonary embolism is ruled out by a D-dimer level of less than 1,000 ng/mL in patients with a low probability, and by a D-dimer level of less than 500 ng/mL in patients with a moderate probability. This way of using D-dimer testing and clinical assessment reduced the need for CT scanning by one-third," said Kearon.

"This was a collaborative study among thrombosis and emergency medicine physicians and researchers. Dr. Kerstin de Wit, who is an emergency medicine and thrombosis specialist, was key to this research and to the study's translation."
The study is funded by the Canadian Institutes of Health Research and endorsed by the Canadian Venous Thromboembolism Clinical Trials and Outcomes Research. It was organized by the Ontario Clinical Oncology Group of McMaster and Hamilton Health Sciences.

Study authors are from McMaster, McGill University, Sherbrooke University, University of Ottawa, Western University and University of Alberta.

Editors: Photos of Dr. Clive Kearon are attached.

Photo caption: Dr. Clive Kearon is a professor of medicine at McMaster University and a thrombosis specialist with Hamilton Health Sciences. Photo courtesy McMaster University

Photo caption: Dr. Clive Kearon (right) and Dr. Kerstin de Wit of McMaster University and Hamilton Heath Sciences. Photo courtesy Hamilton Health Sciences

For more information or to arrange an interview, please contact:

Veronica McGuire
Media Relations
McMaster University
905-525-9140, ext. 22169

Roxanne Torbiak
Public Relations
Hamilton Health Sciences

McMaster University

Related Blood Clots Articles from Brightsurf:

New cause of COVID-19 blood clots identified
A new study reveals that COVID-19 triggers production of antibodies circulating through the blood, causing clots in people hospitalized with the disease.

Children who take steroids at increased risk for diabetes, high blood pressure, blood clots
Children who take oral steroids to treat asthma or autoimmune diseases have an increased risk of diabetes, high blood pressure, and blood clots, according to Rutgers researchers.

COVID-19 may cause deadly blood clots
COVID-19 may increase the risk of blot cots in women who are pregnant or taking estrogen with birth control or hormone replacement therapy, according to a new manuscript published in the Endocrine Society's journal, Endocrinology.

New evidence for how blood clots may form in very ill COVID-19 patients
Neutrophil Extracellular Traps (NETs) have been implicated in causing excessive clotting in cancer patients.

Researchers find new way to detect blood clots
Researchers in the Department of Biomedical Engineering at Texas A&M University are working on an entirely new way to detect blood clots, especially in pediatric patients.

High rate of blood clots in COVID-19
COVID-19 is associated with a high incidence of venous thromboembolism, blood clots in the venous circulation, according to a study conducted by researchers at Brighton and Sussex Medical School (BSMS), UK.

New tool helps distinguish the cause of blood clots
A new tool using cutting-edge technology is able to distinguish different types of blood clots based on what caused them, according to a study published today in eLife.

Hookah smoke may be associated with increased risk of blood clots
In a new study conducted in mice, researchers found that tobacco smoke from a hookah caused blood to function abnormally and be more likely to clot and quickly form blood clots.

Reducing the risk of blood clots in artificial heart valves
People with mechanical heart valves need blood thinners on a daily basis, because they have a higher risk of blood clots and stroke.

New study provides insight into the mechanisms of blood clots in cancer patients
Researchers have identified a potential new signaling pathway that may help further the understanding of blood clot formation in cancer patients and ultimately help prevent this complication from occurring.

Read More: Blood Clots News and Blood Clots Current Events is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to