PE in Pregnancy & YEARS Protocol

So, I generally like the YEARS protocol. It’s an incremental step forwards towards incorporating a pretest likelihood of disease into the interpretation of the D-dimer result. At the least, considering our reckless overdiagnosis of pulmonary embolism, it doesn’t make the situation worse.

Now, pregnancy. There is a mild increase in risk for PE while pregnant, and subsequent puerperal risk is even higher. Unfortunately this leads to a paradox: the index of suspicion for PE during pregnancy is so high, the yield of testing is frighteningly low – on the order of 5% or less for those undergoing evaluation for PE. Little prospective data regarding safe exclusion of PE during pregnancy are available.

These investigators – the Artemis Study – applied the YEARS algorithm, to the diagnosis of PE during pregnancy, attempting generally to demonstrate its safety while describing its yield and test characteristics. The primary modification to the baseline YEARS algorithm was patients having clinical signs of deep-vein thrombosis underwent compression ultrasonography prior to being evaluated with D-dimer and potential CTPA.

They enrolled 498 patients in whom PE was considered a relevant clinical diagnosis, about half of whom met no “high-risk” YEARS criteria. About a fifth of the patients were first trimester, and the remainder were split between second and third. The news is good and bad, unfortunately. Overall, the incidence of PE in their cohort was only 4.0% – typical of our deranged gestalt for PE in pregnancy. In the first trimester, their algorithm excluded PE without CTPA in 65% of those enrolled – meaning only 26 CTPA were indicated to diagnose the 5 PEs in this cohort. This is a reasonable yield.

However, second and third trimester excluded only 46% and 32% of patients from CTPA – meaning 261 CTPAs would be allowed to diagnosis 15 PEs – a yield of only 5.7%. This is better than performing a CT on everyone, but it’s still abysmal. This results, effectively, from the gradual physiologic increase in D-dimer throughout pregnancy – from a median of 505 ng/mL in their first trimester cohort, to 730 and 1,120 in subsequent trimesters.

So, while their algorithm is clearly safe – only one DVT occurred within their 3-month follow-up period, basically the expected rate of occurrence in their enrolled cohort – it’s not the final answer with regard to pregnancy. The next likely step required is to use our observational data to test specific trimester-related normals and pretest-related multipliers to find the optimal cut-offs, such that second and third trimester performance may approach that of the first.

“Pregnancy-Adapted YEARS Algorithm for Diagnosis of Suspected Pulmonary Embolism”
https://www.nejm.org/doi/full/10.1056/NEJMoa1813865