According to Yale researchers, patients being screened for deep vein thrombosis (DVT) using an ultrasound have a rare but serious risk of pulmonary embolism.

The literature review, published in Seminars in Thrombosis and Hemostasis, analyzed over 3,600 articles on DVT screening using ultrasonographic examination of the extremities and of 15 reports of clot dislodgement and embolization they found one probable PE case and seven confirmed PE cases, two of which had fatal outcomes.

Principal investigator and senior author Dr Behnood Bikdeli called PE resulting from DVT ultrasound an “under-recognized and underreported condition,” according to a Yale news release.

Researchers concluded that both clinicians and radiologists need to be more aware of the phenomenon and take precautions. For example, if a patient has a large clot or becomes short of breath after an exam, clinicians should check for the complication. “Be mindful of it,” he said in the Yale news release. “Otherwise, it can lead to a fatal event.”

“Our study also signifies the importance of the search strategy,” Bikdeli added. “A prior systematic review had erroneously claimed that no reports existed about this phenomenon. Clinicians and researchers who look for uncommon or rare clinical events should either develop advanced skills for highly sensitive searching or collaborate with medical librarians who have the expertise of building sophisticated search queries for such purposes.”