YEARS Algorithm and D-Dimer Testing
Yes, all patients screened through the YEARS criteria for PE require a D-dimer test—the D-dimer is integral to the algorithm itself, not a separate decision point. The YEARS algorithm fundamentally combines three clinical items with D-dimer levels to determine who needs imaging 1.
How the YEARS Algorithm Works
The YEARS algorithm consists of three clinical items from the Wells score 1:
- Clinical signs of deep vein thrombosis (DVT)
- Hemoptysis
- PE more likely than an alternative diagnosis
The D-dimer threshold is adjusted based on how many YEARS items are present:
- Zero YEARS items present: PE excluded if D-dimer <1000 ng/mL
- One or more YEARS items present: PE excluded if D-dimer <500 ng/mL
- All other patients proceed to CTPA 1
The algorithm cannot function without the D-dimer—it's not a sequential decision where you first decide whether to order D-dimer, then apply YEARS criteria. Rather, you assess the three clinical items and obtain D-dimer simultaneously, then use both pieces of information together to determine imaging necessity 2.
Special Considerations for Pregnancy
In pregnant patients, the approach differs significantly. The 2011 ATS/STR guidelines explicitly recommend against using D-dimer to exclude PE in pregnancy, citing a sensitivity of only 73% in one study and case reports of false-negative D-dimers in documented PE 3.
However, the 2019 pregnancy-adapted YEARS algorithm (Artemis study) successfully modified the approach for pregnant women 2:
- Same three YEARS clinical criteria apply
- Same D-dimer thresholds (<1000 ng/mL if zero items; <500 ng/mL if ≥1 item)
- Critical addition: Compression ultrasonography performed first if DVT symptoms present—if positive, CTPA avoided entirely
- This safely ruled out PE in 32-65% of pregnant patients (efficiency highest in first trimester, lowest in third trimester) 2
Important Caveats
The ESC guidelines note D-dimer has reduced specificity in several populations 1:
- Cancer patients
- Hospitalized patients
- Severe infection/inflammatory disease
- Pregnancy (D-dimer frequently elevated even without thrombosis)
The number needed to test rises from 3 in general ED populations to >10 in these special situations 1.
Age considerations: While age-adjusted D-dimer cutoffs exist (age × 10 ng/mL for patients >50 years), combining these with YEARS showed no added benefit and resulted in additional missed diagnoses 4. Stick with the standard YEARS thresholds.
Near-threshold results warrant caution: When D-dimer falls within ±0.1 µg/mL of the age-adjusted cutoff, PE prevalence increases with age (28.6% in patients ≥80 years), requiring careful clinical reassessment 5.
Bottom Line
The YEARS algorithm is not a tool to decide whether to order D-dimer—the D-dimer is mandatory for the algorithm to work. The innovation is using variable D-dimer thresholds based on clinical probability rather than a fixed 500 ng/mL cutoff, which safely reduces imaging by approximately 14-39% 1, 6, 2.