Does the IMPROVE clinical prediction model improve stroke risk stratification compared to care-as-usual in patients with symptomatic carotid artery disease?
The IMPROVE model, incorporating MRI-detected intraplaque hemorrhage and conventional risk factors, provides more accurate individual stroke risk estimates than stenosis degree alone in symptomatic carotid artery disease.
BACKGROUND: In symptomatic carotid stenosis, treatment decisions are currently primarily based on stenosis degree. We developed a clinical prediction model (Individualized Magnetic Resonance Imaging-Based Stroke Prediction Score Using Plaque Vulnerability for Patients With Symptomatic Carotid Artery Disease IMPROVE) incorporating the strong predictor, intraplaque hemorrhage on magnetic resonance imaging, stenosis degree, and risk factors to identify patients with high stroke risk. METHODS: IMPROVE was developed on data from 5 cohorts of 760 patients with symptomatic carotid disease on optimal medical treatment. Inclusion criteria included a recent transient ischemic attack/stroke (<6 months), magnetic resonance imaging-based information on intraplaque hemorrhage, no atrial fibrillation, and no immediate revascularization. IMPROVE was based on Cox regression using 5 expert-selected predictors and converted to 3-year ipsilateral ischemic stroke risk after internal validation. IMPROVE-based stratification was compared with care-as-usual using illustrative cutoffs: high risk was defined in IMPROVE as ≥ median 3-year IMPROVE risk, whereas in care-as-usual, it was ≥50% carotid stenosis. RESULTS: Sixty-five ipsilateral ischemic strokes occurred during a median follow-up of 1.2 years (interquartile range, 0.5-4.1). The IMPROVE model includes 5 predictors (hazard ratio 95% CI): degree of stenosis (<50%: reference, 50%-69%: 4.54 2.46-8.38, 70%-99% stenosis: 7.42 3.45-15.95), presence of intraplaque hemorrhage (5.61 2.92-10.77), classification of last event (ocular: reference, cerebral: 3.72 1.11-12.52), male sex (1.26 0.64-2.48), and age (1.14 0.84-1.55 per 10-year increase). Internal validation revealed good accuracy (C statistic, 0.82 95% CI, 0.77-0.87) and no evidence of miscalibration (calibration slope, 0.93). Sensitivity for the illustrative IMPROVE cutoff was 92.6% (90.7-94.5) versus 80.6% (77.8-83.4) for care-as-usual. Specificity was 54.2% (50.7-57.8) for IMPROVE versus 52.9% (49.3-56.4) for care-as-usual. Patients stratified by IMPROVE as high risk had a higher incidence of ipsilateral ischemic stroke (24.0%) compared with the care-as-usual classification (20.7%). Among patients classified as lower-risk by IMPROVE and care-as-usual, 2.1% and 5.3%, respectively, experienced an ipsilateral ischemic stroke during follow-up. CONCLUSIONS: Using the presence of intraplaque hemorrhage on magnetic resonance imaging and 4 conventional parameters, the IMPROVE model provides accurate individual stroke risk estimates, which may facilitate stratification for revascularization after external validation.
Nies et al. (Thu,) studied this question.