Imaging Agent Accurately Identifies Acute Pulmonary Embolism

A new radiolabeled thrombus-specific imaging agent can accurately diagnose acute pulmonary embolism (PE), according to a new study.

Researchers at the University of California, San Diego (UCSD; USA) reported a new method to diagnose acute PE by single photon emission computerized tomography (SPECT) after administration of ^99mTc-labeled antibody fragments that bind to the D-dimer regions of fibrin. The researchers also performed a prospective, multicenter study to investigate the sensitivity and specificity of the new agent, called ThromboView, in 52 subjects with a moderate to high clinical probability of PE. Separate and independent adjudication committees, blinded to clinical data and other test results, interpreted the test results and the thoracic computed tomography (CT) scans.

The results showed that of the 52 patients who were enrolled and completed both tests, 42 had both evaluable SPECT scans and thoracic CT scans. Using the criterion standard (thoracic CT) there were 21 patients with PE and 21 without. Thromboview was found to have a sensitivity of 76.2%, a specificity of 90.5%, a positive predictive value of 88.9%, and negative predictive value of 79.2% for acute PE. The study was published ahead of print on June 16, 2011, in the American Journal of Respiratory and Critical Care Medicine.

“The major advantage of ThromboView is that it utilizes a fundamentally different approach from other methods for detecting PE,” said lead author Timothy Morris, MD, of the division of pulmonary and critical care medicine. “One tangible benefit is the avoidance of iodinated intravenous contrast material, which can be nephrotoxic in many patients and can cause anaphylactoid reactions due to mast cell activation. Neither phenomenon has been observed with ThromboView.”

PE is most often caused by a blood clot in a vein, with the most common cause being a deep vein thrombosis (DVT), which often migrates to the lungs. Less common causes include air bubbles, fat droplets, amniotic fluid, or clumps of parasites or tumor cells. Risk factors include burns, cancer, childbirth, fractures of the hips or thighbone, heart attack or heart surgery, long-term bed rest, severe injury, stroke, surgery, use of birth control pills or estrogen therapy, and a family history of blood clots.

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