MedWire News: The alveolar-arterial (A-a) oxygen gradient
should not be used to assess pregnant women with suspicion of
pulmonary embolism (PE), US researchers caution.
Despite inconsistent evidence on the sensitivity of the A-a
gradient for PE, many physicians use it as a first-line test in
pregnant or postpartum patients to reduce radiation exposure,
explain Aaron Deutsch and co-workers, from the University of South
Florida College of Medicine in Tampa.
To investigate further, the team examined medical charts for 102
pregnant or postpartum women who underwent PE work-up at Tampa
General Hospital between 2002 and 2009, including a computed
tomography pulmonary angiogram (CTPA) and arterial blood gas
test.
Overall, two pregnant patients and 11 postpartum women (within 6
weeks of giving birth) were diagnosed with PE.
Compared with CTPA, the optimal cutoff for A-a gradient was
age-adjusted, and this gave a sensitivity of 76.9%, specificity of
20.2%, and positive and negative predictive values of 80.0% and
11.5%, respectively.
"Unfortunately, the A-a gradient does not appear to have the
sensitivity/specificity necessary to negate radiologic imaging,"
the researchers comment in the American Journal of Obstetrics
and Gynecology.
"Furthermore, the A-a gradient does not have a high enough
predictive value to forego imaging and proceed directly to
treatment in a pregnant and postpartum population."
The team also determined the predictive value of common signs
and symptoms of PE in the patients. Chest pain had the highest
sensitivity and specificity values (70.0% and 72.3%, respectively)
but none of the classical markers were sufficient for diagnosis of
PE.
Deutcsch et al therefore conclude: "We recommend
maintaining a high index of suspicion for PE because it can be a
catastrophic event in pregnancy.
"Prompt radiologic imaging should facilitate rapid diagnosis and
appropriate treatment."
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2010
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