Less than 2 percent of patients hospitalized with syncope have venous thromboembolism (VTE), hint results of a new study from Canada.

“Testing for VTE in patients hospitalized with syncope is not routine, and the results of our study suggest it should not be done routinely for now,” Dr. Amol Verma from St. Michael’s Hospital, University of Toronto, told Reuters Health by email.

As reported online May 8 in JAMA Internal Medicine, Dr. Verma and colleagues did a retrospective cross-sectional study of VTE evaluation and diagnosis in patients hospitalized through the emergency department with syncope at hospitals in Toronto.

Among 1305 such patients, at least one investigation for VTE was performed in 146 patients (11.2 percent), including 120 patients (9.2 percent) who underwent computed tomographic pulmonary angiography (CTPA) or ventilation perfusion (V/Q) scan and/or compression ultrasonography.

Pulmonary embolism (PE) was diagnosed in 11 of 73 patients who had CTPA or V/Q scan, and deep vein thrombosis (DVT) was detected in 10 of 67 patients who had ultrasonography—a diagnostic yield of 15.1 percent and 14.9 percent, respectively.

The overall prevalence of VTE in the cohort was 1.4 percent, consistent with some previous published estimates which range from 0.9 percent to 2.8 percent, the authors say.

However, the Toronto team’s findings differ markedly from results of the Pulmonary Embolism in Syncope Italian Trial (PESIT), recently published in The New England Journal of Medicine, in which the prevalence of PE was 17.3 percent.

Dr. Verma told Reuters Health, “The most important message from our study is that pulmonary emboli are probably not as common in patients with syncope as the PESIT study suggests. More evidence is needed before clinicians change their practice to screen all patients with syncope for PE.”

Dr. Verma added, “The most likely explanation is that the patients included in the PESIT study were different from the patients in our study. This could be because the criteria for hospitalization for patients with syncope could vary substantially in different healthcare systems. Our study included all patients hospitalized with syncope to the general medicine ward at four hospital sites in Toronto, Canada over a four-year period. The fact that our findings were very different from the PESIT study suggests that the PESIT results may not apply broadly to clinical practice around the world.”

“As an internal medicine physician myself, I will be more mindful to assess for VTE in patients with syncope because of the PESIT study but I will not test all patients routinely,” said Dr. Verma.

PESIT trial investigator Dr. Paolo Prandoni of the University of Padua told Reuters Health, “The difference in the study designs is enormous. This study shares the same limitations of the studies published before the Italian PESIT study, making it unsuitable for any attempts to establish the true prevalence of PE in patients hospitalized for their first episode of syncope.”

The study had no commercial funding and the authors have no relevant disclosures.