Interactive tool
Calculate the IMPROVEDD score
Fill in the seven IMPROVE clinical variables and enter the D-dimer value together with your laboratory's upper limit of normal. The calculator shows both scores, with and without the biomarker.
How to use it
Instructions
How the score is built
IMPROVEDD = IMPROVE score + 2 points if D-dimer ≥ 2 × upper limit of normal. The 2-point weight is not arbitrary: it was derived by comparing the hazard ratio of elevated D-dimer with the increase in risk per point of the IMPROVE score in the adjusted Cox model.
D-dimer
- It must be measured at admission, not at discharge.
- The criterion is relative to the upper limit of normal of the laboratory performing the test: there is no universal absolute value. With a ULN of 500 µg/L FEU the threshold is 1000; with a ULN of 250 µg/L DDU the threshold is 500.
- The calculator explicitly asks for both values to avoid the most common error, namely applying another laboratory's threshold.
- In acutely ill medical patients D-dimer is raised in a very large proportion of cases: here it is not used to rule out thrombosis, but as a marker of haemostatic activation and therefore of risk.
When to use it instead of IMPROVE
- When the question is “does this patient need prophylaxis after discharge as well?”. For the in-hospital decision alone, IMPROVE or Padua is sufficient.
- In patients who at discharge still have reduced mobility, active cancer or a prolonged hospital stay.
- Do not use it if D-dimer was not measured at admission: adding the biomarker retrospectively, after days of treatment, does not reproduce the study conditions.
Clinical references
Guidelines and interpretation
| IMPROVEDD score | At 35–42 days | At 77 days |
|---|---|---|
| 0 | 0.4% | 0.5% |
| 1 | 0.6% | 0.7% |
| 2 | 0.8% | 1.0% |
| 3 | 1.2% | 1.4% |
| 4 | 1.6% | 1.9% |
| ≥ 5 | 2.2% | 2.7% |
What it adds to IMPROVE
In the derivation study (Gibson CM. et al., TH Open 2017, 7441 patients from the APEX trial) adding D-dimer improved the model's discrimination and correctly reclassified a substantial proportion of patients. The most clinically useful effect is the move from a score of 1 to a score of 3 in patients with a single clinical factor but markedly raised D-dimer: these are patients whom IMPROVE alone would have classified as low risk.
Elevated D-dimer proved to be an independent predictor of venous thromboembolism (hazard ratio about 2.0) and also of all-cause mortality, making it a general prognostic marker in acutely ill medical patients, not only a thrombotic one.
Extended prophylaxis: the evidence
- APEX (betrixaban 80 mg daily for 35–42 days versus enoxaparin for 10 days): fewer thromboembolic events in the elevated D-dimer subgroup, with no significant increase in major bleeding. Betrixaban is not available in Italy.
- MARINER (rivaroxaban 10 mg daily for 45 days after discharge): the primary outcome was not met, but symptomatic fatal and non-fatal thromboembolism was reduced, with a low rate of major bleeding.
- MAGELLAN (rivaroxaban for 35 days) and ADOPT (apixaban for 30 days): fewer events, offset by an increase in clinically relevant bleeding in the unselected population.
No guideline currently recommends extended thromboprophylaxis after discharge for all medical patients. IMPROVEDD helps identify the subgroup in which the balance may be favourable — score ≥ 2–4, low bleeding risk (IMPROVE Bleeding < 7), risk factors persisting at discharge — as part of an individual decision, discussed with the patient and documented. Also check the availability and licensed indications of the drugs in your own regulatory setting.
In patients with cancer
If active cancer is the dominant factor, the reference model for outpatient prophylaxis is the Khorana score, not IMPROVEDD: the tools were built on different populations and answer different clinical questions.
References
Sources
- Gibson CM. et al., TH Open 2017 — The IMPROVEDD VTE Risk Score: incorporation of D-dimer into the IMPROVE score to improve venous thromboembolism risk stratification.
- Spyropoulos AC. et al., TH Open 2020 — Modified IMPROVE VTE risk score and elevated D-dimer identify a high venous thromboembolism risk in acutely ill medical population for extended thromboprophylaxis.
- Cohen AT. et al., N Engl J Med 2016 — Extended thromboprophylaxis with betrixaban in acutely ill medical patients (APEX).
- Spyropoulos AC. et al., N Engl J Med 2018 — Rivaroxaban for thromboprophylaxis after hospitalization for medical illness (MARINER).
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 is transmitted to or stored on any server.