Risk Assessment Models for Venous Thromboembolism in Medical Inpatients

Abstract

Importance: Thromboprophylaxis is recommended for medical inpatients at risk of venous thromboembolism (VTE). Risk assessment models (RAMs) have been developed to stratify VTE risk, but a prospective head-to-head comparison of validated RAMs is lacking.

Objectives: To prospectively validate an easy-to-use RAM, the simplified Geneva score, and compare its prognostic performance with previously validated RAMs.

Design, setting, and participants: This prospective cohort study was conducted from June 18, 2020, to January 4, 2022, with a 90-day follow-up. A total of 4205 consecutive adults admitted to the general internal medicine departments of 3 Swiss university hospitals for hospitalization for more than 24 hours due to acute illness were screened for eligibility; 1352 without therapeutic anticoagulation were included.

Exposures: At admission, items of 4 RAMs (ie, the simplified and original Geneva score, the Padua score, and the IMPROVE [International Medical Prevention Registry on Venous Thromboembolism] score) were collected. Patients were stratified into high and low VTE risk groups according to each RAM.

Main outcomes and measures: Symptomatic VTE within 90 days.

Results: Of 1352 medical inpatients (median age, 67 years [IQR, 54-77 years]; 762 men [55.4%]), 28 (2.1%) experienced VTE. Based on the simplified Geneva score, 854 patients (63.2%) were classified as high risk, with a 90-day VTE risk of 2.6% (n = 22; 95% CI, 1.7%-3.9%), and 498 patients (36.8%) were classified as low risk, with a 90-day VTE risk of 1.2% (n = 6; 95% CI, 0.6%-2.6%). Sensitivity of the simplified Geneva score was 78.6% (95% CI, 60.5%-89.8%) and specificity was 37.2% (95% CI, 34.6%-39.8%); the positive likelihood ratio of the simplified Geneva score was 1.25 (95% CI, 1.03-1.52) and the negative likelihood ratio was 0.58 (95% CI, 0.28-1.18). In head-to-head comparisons, sensitivity was highest for the original Geneva score (82.1%; 95% CI, 64.4%-92.1%), while specificity was highest for the IMPROVE score (70.4%; 95% CI, 67.9%-72.8%). After adjusting the VTE risk for thromboprophylaxis use and site, there was no significant difference between the high-risk and low-risk groups based on the simplified Geneva score (subhazard ratio, 2.04 [95% CI, 0.83-5.05]; P = .12) and other RAMs. Discriminative performance was poor for all RAMs, with an area under the receiver operating characteristic curve ranging from 53.8% (95% CI, 51.1%-56.5%) for the original Geneva score to 58.1% (95% CI, 55.4%-60.7%) for the simplified Geneva score.

Conclusions and relevance: This head-to-head comparison of validated RAMs found suboptimal accuracy and prognostic performance of the simplified Geneva score and other RAMs to predict hospital-acquired VTE in medical inpatients. Clinical usefulness of existing RAMs is questionable, highlighting the need for more accurate VTE prediction strategies.

Figure 1.. Kaplan-Meier Plot Showing the Cumulative Incidence of Venous Thromboembolism Among Patients at Low and High Risk

A, Simplified Geneva risk score. The cumulative incidence was 1.2% (95% CI, 0.3%-2.2%) for patients at low risk and 2.6% (95% CI, 1.5%-3.6%) for patients at high risk (log-rank P = .09). B, Original Geneva risk score. The cumulative incidence was 1.1% (95% CI, 0.1%-2.0%) for patients at low risk and 2.6% (95% CI, 1.5%-3.6%) for patients at high risk (log-rank P = .07). C, Padua score. The cumulative incidence was 1.4% (95% CI, 0.5%-2.3%) for patients at low risk and 2.8% (95% CI, 1.5%-4.0%) for patients at high risk (log-rank P = .08). D, IMPROVE (International Medical Prevention Registry on Venous Thromboembolism) score. The cumulative incidence was 1.8% (95% CI, 0.9%-2.6%) for patients at low risk and 2.7% (95% CI, 1.1%-4.3%) for patients at high risk (log-rank P = .26).

Figure 2.. Receiver Operating Characteristic (ROC) Curves for Each Risk Assessment Model

The area under the ROC curve was 58.1% for the simplified Geneva score (95% CI, 55.4%-60.7%), 53.8% (95% CI, 51.1%-56.5%) for the original Geneva score, 56.5% (95% CI, 53.7%-59.1%) for the Padua score, and 55.0% (95% CI, 52.3%-57.7%) for the IMPROVE (International Medical Prevention Registry on Venous Thromboembolism) score.