External validation of the IMPROVE-DD risk assessment model for venous thromboembolism among inpatients with COVID-19

Abstract

There is a need to discriminate which COVID-19 inpatients are at higher risk for venous thromboembolism (VTE) to inform prophylaxis strategies. The IMPROVE-DD VTE risk assessment model (RAM) has previously demonstrated good discrimination in non-COVID populations. We aimed to externally validate the IMPROVE-DD VTE RAM in medical patients hospitalized with COVID-19. This retrospective cohort study evaluated the IMPROVE-DD VTE RAM in adult patients with COVID-19 admitted to one of thirteen Northwell Health hospitals in the New York metropolitan area between March 1, 2020 and April 27, 2020. VTE was defined as new-onset symptomatic deep venous thrombosis or pulmonary embolism. To assess the predictive value of the RAM, the receiver operating characteristic (ROC) curve was plotted and the area under the curve (AUC) was calculated. Sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated. Of 9407 patients who met study criteria, 274 patients developed VTE with a prevalence of 2.91%. The VTE rate was 0.41% for IMPROVE-DD score 0–1 (low risk), 1.21% for score 2–3 (moderate risk), and 5.30% for score ≥ 4 (high risk). Approximately 45.7% of patients were classified as high VTE risk, 33.3% moderate risk, and 21.0% low risk. Discrimination of low versus moderate-high VTE risk demonstrated sensitivity 0.971, specificity 0.215, PPV 0.036, and NPV 0.996. ROC AUC was 0.703. In this external validation study, the IMPROVE-DD VTE RAM demonstrated very good discrimination to identify hospitalized COVID-19 patients at low, moderate, and high VTE risk.

An update on the global use of risk assessment models and thromboprophylaxis in hospitalized patients with medical illnesses from the World Thrombosis Day steering committee: Systematic review and meta‐analysis

“…In fact, some of the included models are not adequately validated for medical patients, such as the Caprini score. In contrast, one of the most frequently validated risk assessment models, the IMPROVE, 17 , 21 , 22 is probably too “young” to have been introduced in clinical practice and subsequently described in surveys or in population studies.…”

Use of Anticoagulants in COVID-19: A Review

“…[30][31][32] Subsequently, VTE risk assessment models incorporating elevated D-dimer have been validated in inpatients with COVID-19. 33 Retrospective data from critically ill patients revealed a phenomenon of breakthrough thrombosis despite standard prophylaxis and suggested a strategy of escalated thromboprophylactic dosing in high-risk cohorts. 34 The potential benefit of escalated dosing has been the subject of many randomized controlled trials 35 ; this has been tempered by observational data associating escalated doses of heparin thromboprophylaxis with increased bleeding.…”

Commentary on the 2021 ASH Guidelines on use of anticoagulation in patients with COVID-19 being discharged from the hospital

“…The original weighted and scored IMPROVE-DD VTE RAM was derived in a hospitalized medically-ill population that included patients with viral and other pneumonias, of which the COVID-19 population is a subset of and with a similar median hospital length of stay of 4.5 days 5,6 Secondly, as stated in the seminal work by McGuinn et al on use of clinical decision rules, external validation of these rules need not be prospective in nature but include multiple settings that incorporate a broad spectrum of patients (where indeed this is most likely achieved using retrospective designs) 7 . The IMPROVE-DD VTE RAM has undergone 2 large external validation studies in nearly 19,000 hospitalized COVID-19 patients using the original model cut-offs, with a score of 4 or more predicting a high VTE risk COVID-19 inpatient group, and has shown reasonable discrimination with an area under the curve of ~0.70 8,9 . In another external validation study, the RAM was a strong and independent predictor of thrombosis and mortality in those patients classified as "high risk" 10 .…”