Is Whole Body Imaging Warranted for Thrombocytopenia Caused by a COVID-19 Vaccine?

In a new study looking at the development of immune thrombotic thrombocytopenia in 40 patients who received one dose of the ChAdOx1 nCov-19 vaccine (AstraZeneca), researchers in the United Kingdom found the use of computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound revealed occult thrombosis in 83 percent of patients who had additional testing beyond the area of the presenting complaint. Eight of the 40 patients died, according to the study, which was published in Radiology.

(Editor’s note: The CHAdOx1 n-Cov-19 vaccine is not currently approved by the United States Food and Drug Administration.)

Eighty percent of the patients in the case series had symptoms within two weeks of their first dose of the ChAdOx1 n-Cov-19 vaccine while the remaining 20 percent of patients experienced symptoms between 14 to 28 days after receiving the vaccine. According to the study, 40 percent of the study population had a combination of cerebral venous sinus thrombosis and pulmonary embolism (PE). Overall, the researchers noted that 34 patients had cerebral venous sinus thrombosis, 17 had PE, 11 were diagnosed with deep venous thrombosis, 10 had portomesenteric venous thrombosis and eight patients developed systemic arterial thrombosis.

While acknowledging that international guidance recommends targeted symptom-specific imaging for patients with vaccine-induced immune thrombotic thrombocytopenia (VITT), the study authors note the 20 percent overall mortality rate in their study and the 50 percent mortality rate in cases involving progressive thrombosis. In light of these findings, the study authors suggest that imaging protocols may need to be re-evaluated in this patient population.

“In our study, progressive thrombosis was observed within the first seven days after presentation in a substantial proportion of patients,” wrote Conrad von Stempel, MD, a consultant interventional radiologist affiliated with University College Hospital in London, and colleagues. “These findings emphasize that VITT is a multisystem disorder and suggest that whole-body contrast-enhanced imaging is likely to identify further thrombosis.”

The researchers noted that 73 percent of patients (29 of 40) initially presented with neurological symptoms ranging from blurred vision and severe headache to seizure and collapse. Subsequent CT or MRI venogram revealed cerebral venous sinus thrombosis in all 29 patients, according to von Stempel and colleagues.

Acknowledging the limitations of the retrospective design, the authors also noted that only symptomatic patients who presented to the hospital were included in the study. The study authors pointed out that in cases of vaccine-induced immune thrombotic thrombocytopenia, imaging of those with asymptomatic thrombosis is not routinely done in clinical practice in the United Kingdom. Accordingly, von Stempel and colleagues suggest that occult thromboses may be higher than reported with limited use of whole-body imaging.