However, the anticoagulant medicines used to treat blood clots aren't without risk. In some people, these medications can cause excessive bleeding that can be life-threatening. So, it's important to accurately diagnose pulmonary embolism. "There's a definite downside to treating unnecessarily," Anderson noted.
For the past 30 years, V/Q scanning has been the tool most often used to diagnose pulmonary embolisms. The test requires an injection of a radioactive tracer and the inhalation of radioactive gas. CTPA has been around for about 10 years and also involves using an injected radioactive tracer but doesn't require the inhalation portion included in V/Q scans. The cost of the two procedures is similar, but there's a slightly higher chance of a reaction to the contrast material used in CTPA, and the radiation dose from the imaging technique is higher with CTPA, according to Glassroth.
While CTPA quickly became an accepted alternative, it wasn't clear how the two methods compared to each other. To answer that question, Anderson and his colleagues recruited 1,417 people being treated for symptoms of pulmonary embolism.
Seven hundred and one of the study volunteers had CTPA to rule out pulmonary embolism, while 716 had V/Q scans. Almost 20 percent of those undergoing CTPA were diagnosed with a pulmonary embolism, compared to 14.2 percent of the V/Q volunteers.
A pulmonary embolism was missed in just 0.4 percent of those who had CTPA versus 1 percent of those who had V/Q scanning, according to the study.
"We did confirm that the newer modality (CTPA) was at least as safe as V/Q," said Anderson.
And, although doctors may still be debating which clots need immediate treatment, Glassroth said the good news from this study is that "we have ever-improving capabilities for
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