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D-Dimer in Pregnancy – Can We Trust It?

August 20, 2021

Written by Rebecca White

Spoon Feed
D-dimer can be safely used to rule out venous thromboembolism (VTE) in pregnant adults with non-high pre-test probability (PTP).

Why does this matter?
Pregnancy increases risk for VTE, which is a leading cause of maternal mortality. Though pregnant patients have historically been excluded from VTE research, recent studies (like this and this) suggest that D-dimer can be safely used to rule out VTE in pregnancy. However, international guidelines remain conflicted. If D-dimer is a safe screening test, why not use it to potentially avoid further diagnostic studies that carry risk to mother and fetus?

Stop on a Dimer
This systematic review and meta-analysis included four studies (of 836 patients) that used D-dimer to rule out suspected VTE in pregnant/postpartum adults. Patients included had low/intermediate or unlikely PTP according to a clinical decision tool or regardless of PTP in one study where a tool was not used. The reference standard was ultrasound, CTPA, or VQ scan at baseline and/or three-month follow-up.

Overall, sensitivity (99.5%) and NPV (100%) were high (95%CI 95.0-100.0; I2, 0%; 95%CI 99.19-100.0; I2, 0%). The pooled failure rate (three-month VTE events in patients untreated after negative D-dimer) was 1/312 (0.32%; 95% CI, 0.06-1.83). VTE was present in 7.4% of patients (95% CI, 3.8-12; I2, 83%). A total of 34.2% of patients had a negative D-dimer (95%CI 15.9-55.23; I2, 89%).

I’ll continue to use D-dimer when evaluating non-high-risk pregnant patients with suspected VTE. This could save 1/3 of patients from a radiation or contrast load, with a very low “miss” rate. *We have the YEARS clinical decision tool, which was specifically validated in the pregnant population as a guide to risk stratification at present. You can try it out on MDCalc – just click the button that says pregnant patient to “Yes.” I’d like to see future work on the optimal D-dimer cutoff during pregnancy and maybe even more decision tools to risk stratify.*

Another Spoonful
Want more PE pearls? Bo Stubblefield put together this epic review of the latest recommendations.

D-Dimer to rule out venous thromboembolism during pregnancy: a systematic review and meta-analysis. J Thromb Haemost. 2021 Jun 23. doi: 10.1111/jth.15432. Online ahead of print.

*This section amended from original post.

What are your thoughts?