How this instrument works
Four factors carry the heaviest weight, three points apiece: active cancer, a previous venous clot, reduced mobility (confined to bed or chair rest for three days or more), and a known clotting disorder. Recent trauma or surgery within the last month adds two. Six smaller factors add one point each: age 70 or older, heart or respiratory failure, an acute heart attack or stroke, an acute infection or rheumatologic flare, obesity with a BMI of 30 or above, and ongoing hormonal treatment. A total of 4 or more marks high risk.
Barbar and colleagues published the score in 2010 after following 1,180 patients admitted to a department of internal medicine for up to 90 days, watching for symptomatic clots. Among the 469 patients — about 40 percent of the cohort — who scored 4 or higher and went without preventive treatment, 11.0 percent developed a confirmed clot; among those below the threshold, the rate ran closer to 0.3 percent. That gap is the entire point of screening on admission rather than waiting for symptoms to appear.
This is a genuinely different job from the Wells and Geneva scores also on this site. Those two ask whether a patient who already has symptoms — leg swelling, shortness of breath — likely has a clot right now. Padua asks something earlier: among patients admitted to a medical ward for an unrelated illness, who's quietly building toward a clot that hasn't happened yet, and therefore needs a blood thinner or a compression device as prevention before it does. One is diagnostic; the other is purely preventive, calculated on or shortly after admission, before any clot-related symptom exists.
- Mark any of the four major factors — active cancer, previous VTE, reduced mobility, or a known thrombophilic condition — each worth 3 points.
- Mark recent trauma or surgery within the last month, worth 2 points.
- Mark the six minor factors that apply — age 70+, heart or respiratory failure, acute MI or stroke, acute infection or rheumatologic disorder, obesity (BMI ≥ 30), or ongoing hormonal treatment — each worth 1 point.
- Read the total; 4 or more marks high risk for venous thromboembolism during this admission.
Worked example — four minor factors reaching the threshold
A 72-year-old admitted with a heart failure exacerbation and a concurrent respiratory infection, with a BMI of 32, and no cancer, no prior clot, normal mobility, no clotting disorder, and no recent trauma or surgery. That's age70 (1) + heartRespFailure (1) + acuteInfectionRheum (1) + obesity (1) = 4, with every other field at 0.
Four separate 1-point minor factors reach the same total — 4 — as a single major factor like active cancer scored on its own. That's a genuinely useful feature of the weighting, not a coincidence: the score treats a cluster of moderate risks as just as concerning as one dominant one, and this patient crosses the high-risk threshold and would typically be flagged for pharmacologic or mechanical clot prevention for the remainder of the admission.
Questions
How is Padua different from the Wells or Geneva score?
Wells and Geneva assess a patient who already has symptoms — leg swelling, chest pain, shortness of breath — and ask how likely those symptoms are to represent a clot right now. Padua runs in the opposite direction: it's calculated on hospital admission, before any clot-related symptom exists, to decide who needs preventive treatment. One diagnoses; the other screens ahead of time.
Why do four factors count for three points while others count for one?
Because in the 2010 derivation study, active cancer, a previous clot, reduced mobility, and a known clotting disorder each independently predicted venous thromboembolism far more strongly than the six minor factors — enough that the authors weighted them three times as heavily rather than folding every factor into a flat one-point checklist.
Can several minor factors add up to the same concern as one major factor?
Yes, and it's a real feature of how the score is built, not an edge case to dismiss: four separate one-point factors — say, age 70 or older, heart failure, an acute infection, and obesity — sum to 4, exactly the high-risk threshold, the same total a single major factor plus one minor factor would produce. The scale doesn't care which combination gets a patient there.
What does a score of 4 or higher actually lead to?
In practice, a high-risk result prompts a discussion of pharmacologic prophylaxis — typically a low-molecular-weight heparin or similar agent — or mechanical prevention such as compression devices where blood thinners are contraindicated, continued for the length of the admission. In the original study, high-risk patients who received prophylaxis saw their clot rate drop from 11.0 percent to 2.2 percent.
Does this score apply to surgical patients?
No — Padua was derived and validated specifically in hospitalized medical patients, meaning admissions for conditions like infection, heart failure, or a stroke rather than a planned operation. Surgical patients have their own, separate risk-assessment tools, since the clot risk from surgery itself follows a different pattern than the risk from being acutely ill and immobile in a medical bed.
Why does reduced mobility count as a major factor?
Because immobility — bedrest or chair-rest with only bathroom privileges for three days or more — removes the calf-muscle pump that normally keeps blood moving through the leg veins, one of the most direct mechanical contributors to clot formation. It's grouped with active cancer and a prior clot as one of the four strongest predictors for exactly that reason.
References
- Barbar S, Noventa F, Rossetto V, et al. — J Thromb Haemost, 2010 (PubMed)
- Kahn SR, Lim W, Dunn AS, et al. — CHEST VTE Prevention Guideline, 2012 (PubMed)
Read this first: This instrument computes a screening figure from population formulas — it is not a diagnosis, and it cannot see the whole picture a clinician can. Use it to inform a conversation, not to replace one.