Interactive tool
Calculate the threshold and compare the value
Enter age and D-dimer value. Check your laboratory's unit of measurement: the standard formula is calibrated on fibrinogen equivalent units (FEU); in laboratories reporting in D-dimer units (DDU) values are about half.
How to use it
How to use it
The principle
The rule is simple: above the age of 50 the threshold becomes age × 10 µg/L FEU; up to the age of 50 the conventional threshold of 500 µg/L FEU still applies. A 78-year-old patient therefore has a threshold of 780 µg/L: a value of 620 µg/L, which with the fixed threshold would have been “positive” and triggered a CT pulmonary angiogram, is negative with the age-adjusted threshold.
Essential condition
D-dimer — with any threshold — is used to rule out thromboembolism in patients with a low or intermediate pre-test probability (or “unlikely” in two-level models). When clinical probability is high D-dimer should not even be requested: go straight to imaging, because a negative result does not lower the post-test probability below the safety threshold.
Correct sequence
- Estimate the pre-test clinical probability with a validated tool: Wells for DVT, Geneva or Wells for pulmonary embolism.
- If probability is high → imaging straight away, no D-dimer.
- If probability is low or intermediate → high-sensitivity D-dimer, compared with the age-adjusted threshold.
- D-dimer below the threshold → thromboembolism excluded, no imaging, no anticoagulation.
- D-dimer above the threshold → CT pulmonary angiography (suspected PE) or venous duplex ultrasound (suspected DVT).
Units of measurement
- FEU (fibrinogen equivalent units): conventional threshold 500 µg/L, equivalent to 0.50 mg/L FEU or 500 ng/mL FEU. This is the unit in which the ADJUST-PE and YEARS studies were validated.
- DDU (D-dimer units): values are about half; the conventional threshold corresponds to ~250 µg/L DDU and the formula becomes age × 5.
- If the laboratory report does not state the unit, ask: it is the most frequent error and can lead to discharging a patient with pulmonary embolism.
Clinical reference
Guidelines and interpretation
Supporting evidence
The prospective multicentre ADJUST-PE study (Righini M. et al., JAMA 2014) enrolled 3346 patients with suspected pulmonary embolism: among those aged 75 or over with a non-high clinical probability, the proportion in whom PE could be excluded without imaging rose from 6.4% to 29.7% with the age-adjusted threshold. The 3-month thromboembolic event rate in untreated patients remained below 0.5%, within the conventionally accepted safety margin.
The 2019 ESC guidelines on the diagnosis and management of acute pulmonary embolism recommend the age-adjusted threshold as an alternative to the fixed threshold (class IIa, level B). TheASH 2018 guidelines (American Society of Hematology) and NICE NG158 also recognise its usefulness in older patients.
| Age | FEU threshold | Approximate DDU threshold |
|---|---|---|
| ≤ 50 years | 500 µg/L | 250 µg/L |
| 60 years | 600 µg/L | 300 µg/L |
| 70 years | 700 µg/L | 350 µg/L |
| 80 years | 800 µg/L | 400 µg/L |
| 90 years | 900 µg/L | 450 µg/L |
Conditions that raise D-dimer regardless of thrombosis
A raised D-dimer is never diagnostic: it has a high negative predictive value and a low positive predictive value. It rises in pregnancy and the puerperium, active cancer, infection and sepsis, recent surgery, trauma, burns, disseminated intravascular coagulation, aortic dissection, renal and hepatic failure, heart failure, resolving haematomas and in hospitalised patients in general. In these settings specificity collapses and age adjustment is not enough to restore it.
Alternatives to age adjustment
- Threshold adapted to clinical probability: the YEARS algorithm uses 1000 ng/mL in patients with none of the three criteria and 500 ng/mL in the others; it has also been validated in pregnancy (Artemis study).
- PEGeD (Kearon C. et al., NEJM 2019): threshold 1000 ng/mL with low Wells probability, 500 ng/mL with moderate probability.
- The strategies should not be combined arbitrarily: choose one and apply it consistently within your department's diagnostic pathway.
In pregnancy D-dimer rises progressively with gestational age and adjusting for maternal age is meaningless. The algorithm validated in this population is the pregnancy-adapted YEARS algorithm (Artemis study), which includes compression ultrasound of the legs in patients with signs of DVT.
Bibliography
Sources
- Righini M. et al., JAMA 2014 — Age-adjusted D-dimer cutoff levels to rule out pulmonary embolism: the ADJUST-PE study.
- ESC 2019 — Guidelines for the diagnosis and management of acute pulmonary embolism, European Heart Journal.
- Douma RA. et al., BMJ 2010 — Potential of an age adjusted D-dimer cut-off value to improve the exclusion of pulmonary embolism.
- NICE NG158 — Venous thromboembolic diseases: diagnosis, management and thrombophilia testing.
A quick-reference tool for healthcare professionals. It does not replace the original guidelines, the summaries of product characteristics or the specialist's clinical judgement. All calculations run in the browser: no patient data are transmitted to or stored on a server.