At what IMPROVEDD (Immobility, Malignancy, Pregnancy/puerperium, Recent trauma/surgery, Reduced mobility, Inflammatory bowel disease, Previous DVT/PE, Elderly age) Risk Score should patients receive thromboprophylaxis (pharmacological or mechanical prophylaxis) to prevent Venous Thromboembolism (VTE)?

IMPROVEDD Risk Score Threshold for Thromboprophylaxis

Patients should receive thromboprophylaxis when their IMPROVEDD score is ≥2, which identifies those at heightened risk for VTE with approximately 2.7-fold increased risk compared to lower-risk patients.

Understanding the IMPROVEDD Score

The IMPROVEDD score enhances the original IMPROVE VTE Risk Assessment Model by incorporating D-dimer levels, providing superior risk stratification for hospitalized medical patients 1. The score adds 2 points to the baseline IMPROVE score when D-dimer is ≥2 times the upper limit of normal (ULN) 1.

Base IMPROVE VTE Score Components 2:

• Previous VTE: 3 points
• Known thrombophilia: 2 points
• Lower limb paralysis: 2 points
• Active cancer: 2 points
• Immobilization >7 days: 1 point
• ICU/CCU stay: 1 point
• Age >60 years: 1 point

Risk Stratification and Treatment Thresholds

IMPROVEDD Score ≥2: Initiate Thromboprophylaxis 1

For patients with IMPROVEDD score ≥2 and low bleeding risk, pharmacologic prophylaxis is strongly recommended 2, 3:

• LMWH (enoxaparin 40 mg subcutaneously once daily) 2
• Unfractionated heparin (5,000 units subcutaneously three times daily) 2, 4
• Fondaparinux (2.5 mg subcutaneously once daily) 2

IMPROVEDD Score 0-1: Low Risk 1

Patients with scores 0-1 have significantly lower VTE risk and generally do not require routine pharmacologic prophylaxis 2. The three-month symptomatic VTE rate in this group is only 0.5% 2.

Bleeding Risk Assessment: Critical Modifier

Before initiating pharmacologic prophylaxis, assess bleeding risk using the IMPROVE Bleeding RAM 2, 3. A score ≥7 indicates high bleeding risk (4.1% major bleeding rate vs 0.4% in low-risk patients) 2.

For High VTE Risk (IMPROVEDD ≥2) + High Bleeding Risk (≥7) 3, 4:

• Use mechanical prophylaxis instead of pharmacologic agents
• Intermittent pneumatic compression (IPC) devices preferred over graduated compression stockings 3, 4
• When bleeding risk decreases, substitute pharmacologic for mechanical prophylaxis 2, 4

Duration of Prophylaxis

Continue thromboprophylaxis throughout the period of immobilization or acute hospital stay 2, 4. The American Society of Hematology strongly recommends against extending prophylaxis beyond hospital discharge for medical patients 2, 4.

Comparison with Alternative Risk Models

While the IMPROVEDD score provides enhanced discrimination, the Padua Prediction Score remains a validated alternative 2, 3. The Padua score threshold is ≥4 points for high VTE risk, which corresponds to an 11% VTE incidence without prophylaxis versus 2.2% with prophylaxis (HR 0.13) 2, 5.

The IMPROVEDD score demonstrates superior risk discrimination with improved area under the curve (ΔAUC: 0.06, p=0.0006) and better reclassification metrics compared to the IMPROVE score alone 1.

Critical Pitfalls to Avoid

• Never use aspirin alone as thromboprophylaxis—it is ineffective for VTE prevention 6, 7
• Do not use graduated compression stockings as primary prophylaxis in medical patients 3
• Avoid universal prophylaxis without risk stratification—this approach is explicitly not recommended 3
• Do not overlook bleeding risk assessment—pharmacologic prophylaxis increases bleeding events (RR 1.34) despite reducing PE 3
• Ensure proper continuous application of mechanical devices when used, as intermittent use reduces efficacy 2