D-dimer to rule out PE still valid in pregnancy

The role of D-dimer in investigating PE in pregnancy has been discussed a few times, with its validity as a rule-out test being debated given that pregnancy is considered a risk factor, although not included in the Wells or PERC criteria.

We concluded during one of our sessions that the risk of PE in pregnancy is mainly raised towards the end, and despite the likelihood of pregnancy causing a raised d-dimer, a negative result was still a negative result, and could be used to rule out PE in early pregnancy.

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This has been supported by this systematic review, which concluded that a negative d-dimer and low-moderate risk Well's score appears adequately sensitive to rule out PE in the first two trimesters of pregnancy. The likelihood of having a normal d-dimer level in later pregnancy is slim even in the absence of thromboembolism (quoted as 0-1%), making it fairly useless as a diagnostic test.

There is a consistent finding in all of the studies that D-dimer values are raised in pregnancy. It could therefore be extrapolated that current D-dimer levels would be more sensitive in pregnant women than in non-pregnant women as they are more likely to already have higher D-dimers. A negative D-dimer in this group would be highly suggestive that the patient does not have a PE unless there is strong clinical suspicion.

 

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