D-dimer Positivity in Aortic Dissection
Approximately 98-99% of patients with acute aortic dissection will have a positive D-dimer test (>500 ng/mL). 1, 2
Evidence on D-dimer Sensitivity in Aortic Dissection
The sensitivity of D-dimer for acute aortic dissection has been consistently high across multiple studies:
- The American College of Emergency Physicians clinical policy (2015) reports that D-dimer has a sensitivity of 98% at the commonly used threshold of 0.5 μg/mL 2, 1
- Ohlmann et al. (2006) found a sensitivity of 99% for D-dimer at a cutoff of 400 ng/mL 2
- Sodeck et al. (2007) reported 100% sensitivity at >0.1 μg/mL and 98% sensitivity at >0.5 μg/mL 2
- Suzuki et al. (2009) found a sensitivity of 96.6% (95% CI 90.3% to 99.3%) at 500 ng/mL 2
- Ersel et al. (2010) reported a sensitivity of 96.6% at >0.246 μg/mL 2, 3
- A meta-analysis by Marill (2008) found an overall sensitivity of 94% 2
- A more recent meta-analysis by Asha et al. (2015) reported a pooled sensitivity of 98.0% (95% CI 96.3% to 99.1%) 4
Factors Affecting D-dimer Results in Aortic Dissection
Despite the high sensitivity, it's important to recognize situations where false negatives can occur:
- Thrombosed false lumen: Patients with aortic dissection and thrombosed false lumen exhibit significantly lower D-dimer levels 2, 1
- Intramural hematoma without intimal flap: Can result in normal D-dimer values 2, 1
- Chronicity: Chronic aortic dissection (>2 weeks) may have normal D-dimer levels 1, 3
- Short length of dissection: May result in lower D-dimer values 1
Clinical Implications
The high sensitivity and negative predictive value (96-100%) make D-dimer useful as a rule-out test:
- A negative D-dimer (<500 ng/mL) in low-risk patients can effectively exclude aortic dissection 1
- D-dimer levels positively correlate with the anatomical extension of the dissection 5
- Higher D-dimer levels (>5200 ng/mL) are associated with increased in-hospital mortality 5
Limitations of D-dimer Testing
While sensitivity is high, specificity is poor:
- Specificity ranges from 34% to 56% at common thresholds 2, 1, 5
- Different D-dimer assays may produce different results 1
- Many conditions can elevate D-dimer levels, including pregnancy, recent surgery, trauma, cancer, and infections 1
Summary
The evidence consistently shows that 98-99% of patients with acute aortic dissection will have a positive D-dimer test. The high sensitivity and negative predictive value make D-dimer useful for excluding aortic dissection in low-risk patients, but clinicians should be aware of specific scenarios where false negatives can occur, particularly in cases with thrombosed false lumen, intramural hematoma, or chronic dissection.