IMPEDE VTE score: how the myeloma VTE points add up

The IMPEDE VTE score adds and subtracts points for nine factors to group people with multiple myeloma by their risk of venous thromboembolism (VTE), a blood clot in a vein. A score of 3 or less is low risk, 4 to 7 intermediate and 8 or more high. The paper reported a 6-month VTE incidence of 3.3%, 8.3% and 15.2% for those groups.

Not a medical device. Not a diagnosis or dosing recommendation.

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Infection and VTE calculators
Sanfilippo KM et al. · 2019
The IMPEDE VTE formula
Worked examples
Frequently asked questions

What is the IMPEDE VTE score?

People with multiple myeloma have a raised risk of blood clots, partly from the disease and partly from the medicines used for it. Sanfilippo and colleagues published the IMPEDE VTE score in the American Journal of Hematology in 2019. The name is built from the initials of its factors: Immunomodulatory drug; body Mass index; Pelvic, hip or femur fracture; Erythropoiesis-stimulating drug; Dexamethasone and doxorubicin; Ethnicity; VTE history; Tunneled line; Existing thromboprophylaxis.

Magent's calculator takes the nine factors, adds the points and returns the score, the risk group and the 6-month figure for that group.

This page explains the arithmetic. It doesn't say what a score means for a particular person.

The IMPEDE VTE formula

Score = 4  immunomodulatory drug (IMiD)
      + 1  BMI ≥ 25 kg/m²
      + 4  pelvic, hip or femur fracture
      + 1  erythropoiesis-stimulating drug (ESA)
      + 3  doxorubicin
      + dexamethasone: none 0 · 160 mg or less per month 2 · more than 160 mg per month 4
      − 3  Asian/Pacific Islander
      + 5  VTE before multiple myeloma
      + 2  tunneled line or central venous catheter
      + existing anticoagulant: none 0 · prophylactic −3 · therapeutic −4

not clamped at zero; highest possible 24
≤ 3 low (3.3%) · 4–7 intermediate (8.3%) · ≥ 8 high (15.2%)

Exact expression the calculator uses:

IMPEDE VTE (Sanfilippo 2019 Table 3) = imid (4) + bmi_ge_25 (1) + pelvic_hip_femur_fracture (4) + esa (1) + doxorubicin (3) + dexamethasone (none 0, low 2, high 4; high if total monthly dosing >160 mg) + asian_pacific_islander (-3) + vte_history (5) + tunneled_line (2) + thromboprophylaxis (none 0, prophylactic -3, therapeutic -4); unclamped; <=3 low 3.3%, 4-7 intermediate 8.3%, >=8 high 15.2%

Inputs

Input	Meaning	Points
`imid`	Immunomodulatory drug in use, such as lenalidomide	4
`bmi_ge_25`	Body mass index 25 kg/m² or more	1
`pelvic_hip_femur_fracture`	Pelvic, hip or femur fracture	4
`esa`	Erythropoiesis-stimulating drug in use	1
`doxorubicin`	Doxorubicin in use	3
`dexamethasone`	none, low (160 mg or less per month) or high (more than 160 mg per month)	0, 2 or 4
`asian_pacific_islander`	Asian/Pacific Islander, as used in the paper	−3
`vte_history`	VTE before multiple myeloma	5
`tunneled_line`	Tunneled line or central venous catheter	2
`thromboprophylaxis`	What the patient is already on: none, prophylactic (such as prophylactic LMWH or aspirin) or therapeutic (such as therapeutic LMWH or warfarin)	0, −3 or −4

How the calculation works

Add the points for each factor present.
Subtract 3 for Asian/Pacific Islander and 3 or 4 for an anticoagulant the patient is already taking.
Group the total: 3 or less is low, 4 to 7 intermediate, 8 or more high.

The total isn't raised to zero. A patient with no other factors who is already on therapeutic anticoagulation scores −4, which falls in the low group.

Units

BMI is in kg/m², but the input is a yes/no flag for 25 or more; the calculator doesn't compute BMI. Dexamethasone is grouped by the total mg per month. The other inputs are yes/no or a named choice.

Worked examples

These use Magent's own expected values for the calculator.

Example 1: no factors

Every factor absent; no dexamethasone; no anticoagulant.
Score 0. Group: low. 6-month figure: 3.3%.

Example 2: an immunomodulatory drug

IMiD 4.
Score 4. Group: intermediate. 6-month figure: 8.3%.

Example 3: an IMiD and a fracture

IMiD 4 + pelvic, hip or femur fracture 4.
Score 8. Group: high. 6-month figure: 15.2%.

Example 4: more than 160 mg of dexamethasone per month

Dexamethasone high 4.
Score 4. Group: intermediate.

Example 5: 160 mg of dexamethasone or less per month

Dexamethasone low 2.
Score 2. Group: low.

Example 6: Asian/Pacific Islander

Asian/Pacific Islander −3.
Score -3. Group: low.

Example 7: already on prophylactic anticoagulation

Prophylactic −3.
Score -3. Group: low.

Example 8: already on therapeutic anticoagulation

Therapeutic −4.
Score -4. Group: low.

History of the IMPEDE VTE score

The calculator cites Sanfilippo and colleagues, American Journal of Hematology, 2019 (volume 94, issue 11, pages 1176–1184). The abstract describes building the score in the Veterans Administration Central Cancer Registry among people with multiple myeloma starting chemotherapy, then testing it in an outside group from the SEER-Medicare database. The risk of VTE rose as the score rose. The 3.3%, 8.3% and 15.2% figures are the 6-month cumulative incidence in the group used to build the score.

When it's used

The score describes VTE risk in a person with multiple myeloma, using the medicines and history at the time it is calculated.

Where it's used

The inputs come from the medication list, the history and the body mass index, gathered in hematology clinics.

Who uses it

The person using the calculator answers the nine factors. The calculator adds the points and assigns the group.

Limits of the calculation

The calculator doesn't compute BMI or assign race or ethnicity. Every factor comes from the person entering it.
The anticoagulant input records what the patient is already taking. The calculator doesn't recommend starting, stopping or changing an anticoagulant, and this page doesn't say what to do with a score.
The dexamethasone cut-off is more than 160 mg per month, as in the 2019 paper, not the NCCN 480 mg definition.
The 6-month figures come from one registry group, not a prediction for one person.
It isn't the Khorana score or the SAVED score, and it doesn't establish that a clot is present.

Clinical decisions belong to a qualified clinician who knows the patient.

Khorana score estimates VTE risk across many cancers starting chemotherapy. IMPEDE VTE is specific to multiple myeloma and counts myeloma medicines.

Glossary

VTE: venous thromboembolism, a clot in a deep vein or the lungs.
IMiD: immunomodulatory drug, such as thalidomide, lenalidomide or pomalidomide.
ESA: erythropoiesis-stimulating drug, a medicine that raises red blood cell production.
Thromboprophylaxis: a blood thinner given to prevent clots.
LMWH: low-molecular-weight heparin.

Common mistakes

Raising a negative score to zero. The score can fall below zero.
Using the NCCN dexamethasone definition. The cut-off here is more than 160 mg per month.
Counting both prophylactic and therapeutic anticoagulation. The patient is in one category, and therapeutic subtracts 4.
Counting VTE that happened during myeloma. The history item covers VTE before multiple myeloma.

Source

Sanfilippo KM, et al. Predicting venous thromboembolism in multiple myeloma: development and validation of the IMPEDE VTE score. Am J Hematol. 2019;94(11):1176-1184. DOI: 10.1002/ajh.25603. PMID: 31379000

Frequently asked questions

What does IMPEDE stand for?

Immunomodulatory drug, body mass index, pelvic, hip or femur fracture, erythropoiesis-stimulating drug, dexamethasone and doxorubicin, ethnicity, VTE history, tunneled line and existing thromboprophylaxis.

What are the IMPEDE VTE risk groups?

3 or less is low, 4 to 7 intermediate and 8 or more high.

Why can the IMPEDE VTE score be negative?

Two factors subtract points: Asian/Pacific Islander and an anticoagulant the patient is already on. The total isn't raised to zero.

How is dexamethasone counted?

None scores 0, 160 mg or less per month scores 2, and more than 160 mg per month scores 4.

What is the highest possible score?

24.