Interpretation of D-Dimer Result of 0.29 ug/mL
A D-dimer result of 0.29 ug/mL is normal and effectively rules out venous thromboembolism and acute aortic dissection in patients with low clinical probability. 1
Clinical Significance of Normal D-Dimer
The reported D-dimer value of 0.29 ug/mL (FEU) is below the standard threshold of 0.45 ug/mL indicated in the reference range, signifying a normal result. This has important clinical implications:
- High Negative Predictive Value: A negative D-dimer has excellent negative predictive value (96-100%) for excluding venous thromboembolism (VTE) and acute aortic dissection in patients with low clinical probability 1
- Sensitivity: At the standard threshold of 500 ng/mL (0.5 ug/mL), D-dimer has a sensitivity of 98% for acute aortic dissection 2
- Clinical Decision Making: This normal result can safely exclude VTE in patients with low clinical probability without requiring additional diagnostic imaging 1, 3
Interpreting D-Dimer in Context
While this result is reassuring, proper interpretation requires clinical context:
Pre-test Probability Assessment: The clinical significance depends on the patient's pre-test probability for thromboembolic disease
Potential False Negatives: Certain conditions may result in false-negative D-dimer values despite presence of thrombotic disease:
- Chronicity (symptoms >2 weeks)
- Thrombosed false lumen or intramural hematoma
- Short length of dissection
- Young patient age 2
Clinical Applications
A normal D-dimer result has several important applications:
- VTE Exclusion: In patients with low clinical probability, this result safely excludes deep vein thrombosis and pulmonary embolism 3
- Aortic Dissection: This result helps exclude acute aortic dissection in patients with low clinical probability 2
- Reduced Need for Imaging: A negative D-dimer in low-risk patients can decrease the need for diagnostic imaging 3
Limitations and Considerations
Despite the high negative predictive value, several factors should be considered:
- Assay Variability: Different D-dimer assays may produce different results, and cutoff values are not transferable between methods or institutions 1
- Unit Standardization: The result is reported in Fibrinogen Equivalent Units (FEU), which are approximately twice the value of D-dimer Units (DDU) 1
- Timing: The clinical utility of D-dimer is affected by the timing of the test relative to symptom onset 2
In conclusion, this normal D-dimer result of 0.29 ug/mL provides strong evidence against active thrombotic processes when combined with appropriate clinical assessment, particularly in patients with low pre-test probability for thromboembolic disease.