Can D-dimer (D-dimer) be used to rule out aortic dissection?

D-Dimer for Ruling Out Aortic Dissection

D-dimer can be used to help rule out acute aortic dissection in LOW-RISK patients when measured within 24 hours of symptom onset, using a cutoff of <500 ng/mL, but it should NEVER be used in high-risk patients who require immediate imaging. 1, 2

Risk Stratification is Mandatory Before D-Dimer Testing

You must first calculate a clinical probability score (0-3 points) based on three categories 1:

High-risk conditions (1 point):

• Marfan syndrome or connective tissue disease
• Family history of aortic disease
• Known aortic valve disease or thoracic aortic aneurysm
• Previous aortic manipulation or cardiac surgery 1

High-risk pain features (1 point):

• Abrupt onset
• Severe intensity
• Ripping or tearing quality 1

High-risk examination features (1 point):

• Pulse deficit or systolic blood pressure difference between arms
• Focal neurological deficit with pain
• New aortic diastolic murmur with pain
• Hypotension or shock 1

When D-Dimer Can Be Used

For patients with LOW or INTERMEDIATE clinical probability (score 0-2):

• A negative D-dimer (<500 ng/mL) measured within 24 hours of symptom onset effectively rules out aortic dissection 1, 2
• Sensitivity is 98% (95% CI 96.3-99.1%) with a negative likelihood ratio of 0.05 2
• In low-risk populations (6% prevalence), post-test probability drops to 0.3% with negative D-dimer 2

For patients with HIGH clinical probability (score 3):

• Proceed DIRECTLY to CT angiography—do NOT measure D-dimer 1
• The negative predictive value is inadequate in high-risk patients 1

Critical Timing Considerations

D-dimer MUST be measured within 24 hours of symptom onset:

• Sensitivity remains excellent (96.6%) throughout the first 24 hours 3
• D-dimer levels show negative correlation with time from symptom onset 1
• Never rely on negative D-dimer in patients presenting >24 hours after symptom onset 1

Diagnostic Performance

Sensitivity: 94-100% when measured within 24 hours 1, 3, 4

Specificity: Only 40-67%, making it highly non-specific 1

The high sensitivity makes it useful for ruling OUT disease, but low specificity means positive results require imaging confirmation 2

Critical Pitfalls: When D-Dimer Will Be Falsely Negative

Never assume negative D-dimer excludes these conditions:

• Intramural hematoma (IMH) without intimal flap—frequently produces negative D-dimer results 1, 5
• Thrombosed false lumen—significantly lowers D-dimer levels and increases false-negative risk 1
• Short dissection length and young patient age—associated with false-negative results 1
• Delayed presentation (>24 hours)—D-dimer levels decline over time 1

Why D-Dimer is Elevated (Low Specificity)

D-dimer cannot differentiate aortic dissection from other acute conditions 1:

• Pulmonary embolism (mean 28.5 mg/mL vs 32.9 mg/mL in dissection) 1
• Acute myocardial infarction 1
• Sepsis 1
• Disseminated intravascular coagulation 1
• Malignancies 1
• Recent trauma or surgery 1
• Following fibrinolytic therapy 1

Clinical Algorithm

1. Calculate clinical probability score (0-3 points) 1

2. If score = 3 (high-risk): Proceed directly to CT angiography—do NOT measure D-dimer 1

3. If score = 0-2 (low/intermediate-risk) AND <24 hours from symptom onset:

   • Measure D-dimer with 500 ng/mL cutoff 1, 2
   • If D-dimer <500 ng/mL: Aortic dissection effectively ruled out 1, 2
   • If D-dimer ≥500 ng/mL: Proceed to CT angiography 1

4. If >24 hours from symptom onset: Do NOT use D-dimer; proceed to imaging if clinical suspicion exists 1

Prognostic Value (If Dissection Confirmed)

• D-dimer >5200 ng/mL independently predicts in-hospital mortality (OR 5.38) 1
• In-hospital D-dimer ≥9 mg/L independently predicts in-hospital mortality (OR 5.60) 1
• Higher levels correlate with anatomical extension and early complications 1