Question 1

What is the age-adjusted D-dimer cutoff?

Accepted Answer

For patients over age 50, the cutoff is age × 10 ng/mL FEU (so a 70-year-old has a cutoff of 700 ng/mL instead of the standard 500). For DDU-reporting assays it is age × 5. Below age 50 the standard 500 ng/mL FEU cutoff is used.

Question 2

When should I use age-adjusted D-dimer?

Accepted Answer

Use it when a patient is older than 50 with low or moderate pretest probability of PE or DVT. With high pretest probability, D-dimer should not be used to rule out — proceed directly to CT angiography or compression ultrasound.

Question 3

Is age-adjusted D-dimer safe?

Accepted Answer

The ADJUST-PE study (JAMA 2014) prospectively validated the strategy: the 3-month VTE rate among ruled-out patients was 0.3%, comparable to standard rule-out, while increasing the proportion of older patients in whom imaging could be avoided. It is endorsed by ACEP, ESC, and the American College of Radiology.

Question 4

What's the difference between FEU and DDU D-dimer units?

Accepted Answer

FEU (fibrinogen-equivalent units) and DDU (D-dimer units) measure the same biology with different reference standards. DDU values are approximately half of FEU values. The standard cutoff is 500 ng/mL FEU or 250 ng/mL DDU; check which your lab reports.

Question 5

Does age-adjusted D-dimer apply in pregnancy?

Accepted Answer

No. Pregnancy raises D-dimer by trimester, and age-based adjustment does not address the pregnancy-related rise. Pregnancy-specific algorithms (YEARS pregnancy adaptation, Artemis) use different rules and are usually reserved for institutional protocols.

Age-Adjusted D-Dimer

References

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