From the Journals

Algorithm ruled out PE, averts radiation exposure in pregnant women


FROM The New England Journal of Medicine

A diagnostic algorithm adapted for use in pregnancy safely ruled out acute pulmonary embolism in nearly 500 women with suspected pulmonary embolism enrolled in a recent prospective study, investigators are reporting.

Using the adapted algorithm, there was only one deep-vein thrombosis (DVT) and no pulmonary embolism (PE) in follow-up among those women, according to the investigators, including senior author Menno V. Huisman, MD, PhD, of the department of thrombosis and hemostasis at Leiden (Netherlands) University Medical Center and his coauthors.

Pulmonary embolism Courtesy Wikimedia Commons/Walter Serra, Giuseppe De Iaco, Claudio Reverberi, and Tiziano Gherli/Creative Commons License

Pulmonary embolism

The main advantage of the algorithm is that it averted CT pulmonary angiography in nearly 40% of patients, thus sparing radiation exposure to mother and fetus in many cases, the investigators added.

“Our algorithm provides solid evidence for the safe management of suspected PE in pregnant women, with selective use of CT pulmonary angiography,” Dr. Huisman and colleagues said in their March 21 report in the New England Journal of Medicine.

In a previous clinical trial, known as the YEARS study, a specialized diagnostic algorithm had a low incidence of failure in men and women with clinically suspected PE, as shown by a venous thromboembolism (VTE) rate of just 0.61% at 3 months and by use of CT pulmonary angiography that was 14 percentage points lower than with a conventional algorithmic approach.

For the current study, Dr. Huisman and his coinvestigators took the YEARS algorithm and adapted it for use in pregnant women with suspected PE presenting at 1 of 18 centers in the Netherlands, France, and Ireland.

Their adapted algorithm was based on the three criteria investigators said were most predictive in the YEARS trial, namely, clinical signs of symptoms of DVT, hemoptysis, and PE as the most likely diagnosis. Patients also underwent D-dimer testing, and if they had clinical signs and symptoms of DVT, underwent compression utrasonography of the symptomatic leg.

Pulmonary embolism was considered ruled out in patients who met none of the three YEARS criteria and had a D-dimer under 1,000 ng/mL, or if they met one to three YEARS criteria and had a D-dimer under 500 ng/mL. Otherwise, patients underwent CT pulmonary angiography and started anticoagulant treatment if results of that test indicated PE.

The primary endpoint of the study was the cumulative 3-month incidence of symptomatic VTE among patients with PE ruled out by this algorithm.

Of 498 patients participating in the study, 477 (96%) had a negative result on the adapted YEARS algorithm at baseline, while 20 (4.0%) received a diagnosis of PE, according to results of the study. One patient was lost to follow-up.

Of the 477 patients with negative results, 1 patient (0.21%) had a diagnosis of symptomatic DVT over the 3 months of follow-up, investigators reported, adding that there were no PE diagnoses over the follow-up period.

That patient with the DVT diagnosis met none of the three YEARS criteria and had a D-dimer level of 480 ng/mL, and so did not undergo CT pulmonary angiography, investigators said.

In the worst-case scenario, the VTE incidence would have been 0.42%, assuming the one patient lost to follow-up would have had a VTE diagnosis over the 3-month follow-up period, they added.

“These data meet the proposed criteria for assessing the safety of diagnostic methods in VTE, even in the context of a low baseline prevalence of disease,” Dr. Huisman and his colleagues wrote.

Overall, CT pulmonary angiography was avoided – avoiding potential radiation exposure-related harms– in 39% of the patients, the investigators said, noting that the proportion of women avoiding the diagnostic test decreased from 65% for those evaluated in the third trimester, 46% in the second trimester, and 32% in the third.

“This decreasing specificity can be explained by the physiological rise in the D-dimer level that commonly occurs during pregnancy,” said Dr. Huisman and his coauthors.

The study was supported by unrestricted grants from Leiden University Medical Center and 17 other participating hospitals. Many authors reported financial ties to the pharmaceutical industry.

SOURCE: van der Pol LM et al. N Engl J Med. 2019;380:1139-49

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