D-Dimer in Acute Aortic Syndrome
D-dimer testing cannot be recommended for routine screening of all patients being evaluated for acute aortic dissection, but a negative D-dimer (<500 ng/mL) within 24 hours of symptom onset can help rule out the diagnosis in patients without high-risk clinical features. 1
Diagnostic Performance
Sensitivity and Limitations
D-dimer demonstrates high sensitivity (94% pooled sensitivity, 95% CI 91-96%) for acute aortic dissection, with some studies showing 100% sensitivity when measured within 24 hours of symptom onset. 1, 2, 3
The negative likelihood ratio of 0.07 when using the 500 ng/mL cutoff suggests that a negative result can effectively rule out aortic dissection in appropriate clinical contexts. 2
Critical caveat: D-dimer cannot be used to rule out disease in high-risk patients, as the negative likelihood ratio is insufficient in this population. 1
Conditions Causing False-Negative Results
Intramural hematoma (IMH) without intimal flap may produce negative D-dimer results. 1, 4
Thrombosed false lumen significantly lowers D-dimer levels and increases risk of false-negative results. 1, 4
Younger patients with short dissection length and thrombosed false lumens without ulcer-like projections are at higher risk for false-negative results. 1
High platelet count and low extension score are independent factors associated with negative D-dimer despite presence of dissection. 5
Time from symptom onset shows negative correlation with D-dimer levels—delayed presentations may have falsely negative results. 1, 4
Specificity Issues
Non-Specific Elevation
D-dimer specificity ranges from only 40% to 100%, making it highly non-specific for aortic dissection. 1
D-dimer elevates in multiple conditions including pulmonary embolism, acute myocardial infarction, sepsis, disseminated intravascular coagulation, malignancies, recent trauma or surgery, and following fibrinolytic therapy. 1, 4
D-dimer cannot reliably differentiate acute aortic dissection (mean 32.9 mg/mL) from pulmonary embolism (mean 28.5 mg/mL). 1
Routinely obtaining D-dimer in large populations with symptoms suspicious for aortic dissection can result in harm through unnecessary radiation exposure and cost from advanced imaging. 1
Clinical Application Algorithm
When to Consider D-Dimer Testing
D-dimer may be considered in patients with intermediate clinical suspicion for aortic dissection, but NOT in high-risk patients where imaging should proceed directly. 1, 4, 6
Testing should only be performed within 24 hours of symptom onset for optimal negative predictive value. 2, 3
High-Risk Features Requiring Direct Imaging (Bypass D-Dimer)
Patients with any of the following should proceed directly to CT angiography: 1
- Pain characteristics: Abrupt/instantaneous onset, severe intensity, ripping/tearing/stabbing quality
- Physical examination findings: Pulse deficit, systolic blood pressure limb differential >20 mmHg, focal neurologic deficit, new murmur of aortic regurgitation
- Risk factors: Marfan syndrome, Loeys-Dietz syndrome, vascular Ehlers-Danlos syndrome, Turner syndrome, family history of aortic disease, recent aortic manipulation
Interpretation Strategy
A negative D-dimer (<500 ng/mL) in a patient without high-risk features, presenting within 24 hours, can help exclude aortic dissection. 2, 3
Any positive D-dimer result requires definitive imaging with CT angiography—it cannot confirm the diagnosis. 1, 6
In patients over 50 years, consider age-adjusted D-dimer cutoffs (age × 10 μg/L) to improve specificity. 4, 6
Critical Pitfalls to Avoid
Never use D-dimer to rule out aortic dissection in high-risk patients—the negative predictive value is inadequate in this population. 1
Never rely on a negative D-dimer alone in patients presenting >24 hours after symptom onset, as levels decline over time. 1, 4
Never assume a negative D-dimer excludes IMH or dissection with thrombosed false lumen—these conditions frequently have false-negative results. 1, 4
Never use D-dimer in hospitalized or acutely ill patients due to high frequency of false-positive results. 4, 7
Emergency operations are necessary in 33% of patients with negative D-dimer results who have type A dissection with cardiac tamponade—clinical judgment supersedes laboratory testing. 5
Prognostic Value
Higher D-dimer levels correlate with patients who died early, underwent emergency procedures, or had complications. 1
D-dimer levels are higher in acute versus chronic dissections. 1, 4
The degree of elevation correlates with time from symptom onset but shows only a trend toward correlation with dissection extent. 3