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Complete lower limb venous ultrasound (US) has
higher sensitivity and capacity to exclude pulmonary embolism (PE),
but a lower specificity in comparison to limited US, new research
suggests.
In patients with clinically suspected acute PE, a limited US confined
to the popliteal and femoral veins is usually performed to detect
residual deep vein thrombosis (DVT), a finding that is highly suggestive
of PE.
However, the prevalence of DVT detected by limited US is low. Antoine
Elias, MD, PhD, of the Department of Vascular Medicine, Rangueil
University Hospital Centre, Toulouse, France, and colleagues assessed
the diagnostic performance of complete US examining the proximal
and distal veins against a reference diagnostic strategy in 210
consecutive patients with clinically suspected acute PE.
Prior to diagnostic testing, patients were clinically assessed for
the probability of PE and classified as high (compatible symptoms/signs
of PE, 1 or more risk factors, and no alternative diagnosis), low
(less compatible symptoms/signs of PE, no risk factors, an alternative
diagnosis available), and intermediate (all other cases).
The combination of clinical probability, ventilation perfusion scan
(V/Q scan), and pulmonary angiography in the brachial vein, including
a 3-month follow up, was used as the reference diagnostic strategy.
The reference strategy was compared with results obtained from simultaneous
assessment with complete bilateral US, VIDAS D-dimer (DD) assay,
and helical computed tomography (HCT) of the lungs.
Results showed that complete US detected venous thrombosis in 43.3%
of patients compared to 22% that would have been detected by limited
US. Compared with the reference strategy, complete US sensitivity
and specificity was 0.93 [0.85 - 0.97] and 0.84 [0.77 - 0.89], respectively,
and 0.55 [0.44 - 0.66] and 0.96 [0.92 - 0.98] for limited US.
Furthermore, complete US results compared favourably with HCT and
DD results. Sensitivity and specificity were 0.92 [0.83 - 0.96]
and 0.24 [0.17 - 0.32], respectively, for DD with a 500 ng/mL cut
off value, and 0.84 [0.73 - 0.90] and 0.87 [0.80 - 0.92], respectively,
for HCT.
According to the researchers, the detection of isolated calf thrombi
may be important to the management of PE for both diagnostic and
prognostic reasons, and they conclude that the utility of complete
US in diagnostic strategies for PE should be assessed in large outcome
studies.
The Regional Delegation for Clinical Research and Pharmacia Upjohn
provided financial support for the study.
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