Coagulation
D-dimer
Fibrin degradation fragment; sensitive but non-specific marker of active fibrinolysis.
Sample
Citrated plasma
Clinical reference range
— to 500 ng/mL FEU
Conventional · Age-adjusted: age × 10 (>50 y)
Conv: —–500 ng/mL FEU
Biology
What it measures
Released when cross-linked fibrin is cleaved by plasmin. Indicates that thrombus has formed AND is being broken down.
Clinical use
Why we order it
Rule-out VTE/PE in low-to-moderate pretest probability. DIC workup. Aortic dissection screening.
Lens · Clinical
Interpretation by lens
Clinical interpretation
Negative D-dimer + low Wells score safely excludes PE without imaging (PERC/YEARS algorithms refine this further).
Differential
Causes of abnormal values
Causes of HIGH
- ↑VTE / PE
- ↑DIC
- ↑Aortic dissection
- ↑Sepsis / inflammation
- ↑Recent surgery or trauma
- ↑Pregnancy
- ↑Malignancy
- ↑Advanced age
- ↑Liver disease
Pitfalls
Pre-analytic & interpretation traps
- !Use only to rule-OUT in low pretest probability (Wells/Geneva); never to rule-IN.
- !Two reporting units exist — DDU and FEU. FEU ≈ 2× DDU. Misreading the unit causes major misinterpretation.
- !Apply age-adjusted cutoff in patients >50 y to improve specificity (age × 10 ng/mL FEU).
Related