From the Journals

D-dimer thresholds rule out PE in meta-analysis



Adapted D-dimer thresholds based on pretest probability were effective for ruling out pulmonary embolism (PE) in subgroups of high-risk individuals without the use of imaging in a review of data.

In a patient suspected to have a PE, “diagnosis is made radiographically, usually with CT pulmonary angiogram, or V/Q scan,” Suman Pal, MD, of the University of New Mexico, Albuquerque, said in an interview.

“Validated clinical decision tools such as Wells’ score or Geneva score may be used to identify patients at low pretest probability of PE who may initially get a D-dimer level check, followed by imaging only if D-dimer level is elevated,” explained Dr. Pal, who was not involved with the new research, which was published in the Annals of Internal Medicine.

According to the authors of the new paper, while current diagnostic strategies in patients with suspected PE include use of a validated clinical decision rule (CDR) and D-dimer testing to rule out PE without imaging tests, the effectiveness of D-dimer tests in older patients, inpatients, cancer patients, and other high-risk groups has not been well-studied.

Lead author of the paper, Milou A.M. Stals, MD, and colleagues said their goal was to evaluate the safety and efficiency of the Wells rule and revised Geneva score in combination with D-dimer tests, and also the YEARS algorithm for D-dimer thresholds, in their paper.

Dr. Stals, of Leiden (the Netherlands) University Medical Center, and the coinvestigators conducted an international systemic review and individual patient data meta-analysis that included 16 studies and 20,553 patients, with all studies having been published between Jan. 1, 1995, and Jan. 1, 2021. Their primary outcomes were the safety and efficiency of each of these three strategies.

In the review, the researchers defined safety as the 3-month incidence of venous thromboembolism after PE was ruled out without imaging at baseline. They defined efficiency as the proportion patients for whom PE was ruled out based on D-dimer thresholds without imaging.

Overall, efficiency was highest in the subset of patients aged younger than 40 years, ranging from 47% to 68% in this group. Efficiency was lowest in patients aged 80 years and older (6.0%-23%), and in patients with cancer (9.6%-26%).

The efficiency was higher when D-dimer thresholds based on pretest probability were used, compared with when fixed or age-adjusted D-dimer thresholds were used.

The key finding was the significant variability in performance of the diagnostic strategies, the researchers said.

“The predicted failure rate was generally highest for strategies incorporating adapted D-dimer thresholds. However, at the same time, predicted overall efficiency was substantially higher with these strategies versus strategies with a fixed D-dimer threshold as well,” they said. Given that the benefits of each of the three diagnostic strategies depends on their correct application, the researchers recommended that an individual hospitalist choose one strategy for their institution.

“Whether clinicians should rely on the Wells rule, the YEARS algorithm, or the revised Geneva score becomes a matter of local preference and experience,” Dr. Stals and colleagues wrote.

The study findings were limited by several factors including between-study differences in scoring predictors and D-dimer assays. Another limitation was that differential verification biases for classifying fatal events and PE may have contributed to overestimation of failure rates of the adapted D-dimer thresholds.

Strengths of the study included its large sample size and original data on pretest probability, and that data support the use of any of the three strategies for ruling out PE in the identified subgroups without the need for imaging tests, the authors wrote.

“Pending the results of ongoing diagnostic randomized trials, physicians and guideline committees should balance the interlink between safety and efficiency of available diagnostic strategies,” they concluded.


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