What to do with a patient with a normal D-dimer (D-dimer) level?

Management of a Patient with D-dimer of 0.67

A D-dimer value of 0.67 μg/mL is considered normal and effectively rules out venous thromboembolism (VTE) in patients with low or intermediate clinical probability, requiring no further testing or anticoagulation.

Understanding D-dimer Values and Interpretation

D-dimer is a fibrin degradation product that results from the degradation of blood clots through fibrinolysis. It serves as a biomarker for activation of coagulation and fibrinolysis 1.

• Normal D-dimer value: <0.5 μg/mL (500 ng/mL)
• Your patient's value: 0.67 μg/mL

While this is slightly above the traditional cutoff, several important considerations apply:

Age-Adjusted D-dimer Cutoffs

The European Society of Cardiology recommends age-adjusted D-dimer cutoffs for patients over 50 years 2, 3:

• Age-adjusted cutoff = Age × 10 ng/mL (or Age × 0.01 μg/mL)
• For example:
  • 60-year-old patient: cutoff would be 600 ng/mL (0.6 μg/mL)
  • 70-year-old patient: cutoff would be 700 ng/mL (0.7 μg/mL)

If your patient is over 67 years old, the D-dimer value of 0.67 would be considered normal using age-adjusted cutoffs.

Clinical Decision Algorithm

1. Assess clinical probability of VTE:

   • Use validated tools like Wells score or Geneva score
   • For low-risk patients, consider PERC criteria

2. Interpret D-dimer based on clinical probability:

   • For low/intermediate probability + normal D-dimer (including age-adjusted): No VTE, no further testing needed
   • For low/intermediate probability + elevated D-dimer: Proceed to imaging
   • For high probability: Proceed directly to imaging regardless of D-dimer

3. For your patient with D-dimer of 0.67:

   • If patient is ≥67 years old: Value is normal using age-adjusted cutoff
   • If patient is <67 years old: Value is slightly elevated, but clinical context matters

Special Considerations

YEARS Algorithm

The YEARS clinical decision rule can also be applied 2:

• If no YEARS criteria present (no signs of DVT, no hemoptysis, PE not most likely diagnosis), use D-dimer cutoff of 1000 ng/mL
• If ≥1 YEARS criteria present, use traditional cutoff of 500 ng/mL

Clinical Contexts Affecting D-dimer

D-dimer may be elevated in various conditions without indicating thrombosis 2, 3:

• Pregnancy
• Advanced age
• Hospitalization
• Cancer
• Infection/inflammation
• Recent surgery or trauma

Key Pitfalls to Avoid

1. Not using age-adjusted cutoffs in older patients, which can lead to unnecessary imaging
2. Relying solely on D-dimer for VTE diagnosis rather than combining with clinical probability
3. Ignoring extremely elevated values (>5000 μg/mL), which are highly specific for serious conditions including VTE, sepsis, and cancer 4
4. Using D-dimer inappropriately in patients with high clinical probability of VTE, where imaging should be performed regardless of D-dimer result

Bottom Line

For a patient with D-dimer of 0.67 μg/mL:

• If ≥67 years old: No further testing needed if clinical probability is low/intermediate
• If <67 years old: Consider imaging if clinical probability is not low, especially if other risk factors are present
• If clinical probability is high: Proceed directly to appropriate imaging regardless of D-dimer result

Remember that D-dimer has excellent negative predictive value but poor positive predictive value for VTE 2. A normal D-dimer effectively rules out VTE in low to intermediate risk patients, but an elevated D-dimer requires further diagnostic workup.