A review on the evolution of d-dimer use in ruling out pulmonary embolism in the ED and the supporting evidence to increase the upper limit of a negative value.
Last updated 12/11/24
The PERC rule and avoiding further testing
- PERC Rule for PE (MDCalc)
- A validated clinical decision rule to safely exclude PE without diagnostic testing or imaging in patients meeting all criteria. It can only be applied if pre-test probability ≤ 15%.
- Wells Criteria for PE (MDCalc)
- A validated score that predicts pre-test probability of PE risk stratifying patients into two different models
- Three tier system - Low, moderate or high risk (with associated % risk)
- Two tier system - PE unlikely or PE likely.
- Basic algorithm
- Apply Wells Criteria → if risk ≤ 15% → apply PERC rule → if negative, PE ruled out
Wells Score and D-Dimer
- The classic teaching is calculating a Wells Score (MDCalc), risk stratifying using the two-tier system and applying d-dimer if appropriate.
- Wells Score ≤ 4 → PE “unlikely” → use D-dimer
- Wells score ≥ 5 → PE “likely” → use CTA
- In Depth explanation
- REBEL EM: Wells and D-Dimer to Rule Out PE
- Primary literature: Excluding pulmonary embolism at the bedside without diagnostic imaging
🧓 Age-Adjusted D-Dimer
- The age adjusted d-dimer (MDCalc) increases the upper limit of a negative value based on the patient’s age. Remember different assays have different adjustments.
- DDU cut off = age x 5 ng/mL
- FEU cut off = age x 10 ng/mL
- FOAMed explanations
- CORE EM: Age-Adjusted D-Dimer (Part 1)
- CORE EM: Age-Adjusted D-Dimer (Part 2)
YEARS Algorithm and Using Higher D-Dimer Cutoffs
The validated YEARS algorithm (MDCalc) pushes the upper limit of a negative d-dimer even further.
- D-dimer cutoffs
- 500/1000 ng/mL for FEU
- 250/500 ng/mL for DDU (1/2 FEU)
- It is important to adjust the cutoff limits if using DDU
- In Depth Explanations
- REBEL EM: The YEARS Study
- Primary Literature: original YEARS study in the Lancet
- Primary Literature: AEM validation study
- Primary Literature: JAMA validation study
đź«„YEARS Algorithm and Pregnancy
- This prospective study published in NEJM was a groundbreaking study that applied the pregnancy-adapted YEARS algorithm to rule out PE in pregnancy and limit radiation exposure. (see below)
- FOAMed explanations
- REBEL EM: Pregnancy-Adapted YEARS Algorithm
- JournalFeed: PE in Pregnancy - YEARS Algorithm
- SGEM: Diagnosing PE in Pregnancy
🧩 Putting it all together and combining strategies
- Consider the following algorithm to identify your d-dimer cutoff.
- Low risk: Use Wells + PERC to rule out PE w/o further testing
- Low-moderate risk
- YEARS 0 → use 500 ng/mL (DDU) or 1000 ng/mL (FEU) dimer cutoff
- Do not apply age adjusted cutoff unless your patient is > 100 years old which would yield a higher cutoff
- YEARS ≥ 1 → use 250 ng/mL (DDU) or 500 ng/mL (FEU) dimer cutoff
- OR age adjusted cutoff if patient > 50 years old (this will yield a higher cutoff level)
- For pregnancy → use YEARS pregnancy adapted algorithm
- For high risk patients → CTA
- FOAMed
- REBEL EM: Pragmatic Combination of YEARS and Age-Adjusted D-Dimer
- Clinical Monster: Working up PE in the ED (by Dr. Noah Berland)
- JournalFeed: The ideal PE Rule-Out Study