What Constitutes High Risk for Venous Thromboembolism? Comparing Approaches to Determining an Appropriate Threshold

Area of Science:

• Internal Medicine
• Clinical Pharmacology
• Epidemiology

Background:

• Current guidelines recommend pharmacological venous thromboembolism (VTE) prophylaxis for high-risk patients, but lack a defined probability threshold for risk stratification.
• This ambiguity leads to variability in prophylaxis decisions for medical inpatients.

Purpose of the Study:

• To define an appropriate probability threshold for VTE risk stratification and corresponding prophylaxis in medical inpatients.
• To compare different methodologies for establishing this threshold.

Main Methods:

• A cohort of 41,036 adult inpatients across 10 hospitals was analyzed.
• Five distinct approaches were used to determine VTE risk probability thresholds, including decision analysis, logistic regression, a point-based model, and physician surveys/behavior analysis.
• The Cleveland Clinic VTE risk assessment model (CCM) was applied to the cohort using the derived thresholds.

Main Results:

• The analyzed approaches yielded VTE risk thresholds ranging from 0.3% to 5.4%.
• Multiple methods converged on a threshold cluster between 0.52% and 0.55%, suggesting a hypothetical prophylaxis rate of approximately 30%.
• Physicians' observed prophylaxis rates (48%-76%) significantly exceeded this suggested rate, indicating potential for overtreatment.

Conclusions:

• An optimal probability threshold for VTE prophylaxis in medical inpatients is approximately 0.5%.
• Current clinical practice involves more frequent prophylaxis than indicated by this threshold, suggesting a need for optimization.
• Guidelines should explicitly quantify high-risk VTE probabilities to standardize prophylaxis decisions and reduce unnecessary treatments.