Age-adjustment of the combined early ischemic change and collateral extent score for outcomes after endovascular therapy

BACKGROUND: Both age and ischemic core volume are strong predictors of outcomes after endovascular therapy. We previously developed and reported the ASPECTS and the multiphase CTA collateral extent (mCTA-ACE) score, which combines early ischemic changes on NCCT and the extent of leptomeningeal filling on multiphase CTA, and showed that it was associated with outcomes after EVT. The aim of this study was to refine the mCTA-ACE score through age adjustment and external validation. METHODS: We performed a post hoc analysis of endovascular therapy-treated patients from the AcT (Alteplase Compared to Tenecteplase) trial. The mCTA-ACE score was calculated as the baseline ASPECTS plus a 10-point mCTA collateral score, corresponding to ASPECTS regions M2–M6 graded as poor (0), moderate (1), or normal (2). From the mixed-effect logistic regression for mRS ≤2 at 90–120 days, the relative regression coefficient of age to mCTA-ACE score was used to derive the age-adjusted mCTA-ACE score. The prediction ability of age-adjusted mCTA-ACE score was validated in a reduced model from the PRove-IT (Precise and Rapid Assessment of Collaterals Using Multi-Phase CTA in the Triage of Patients With Acute Ischemic Stroke for IA Therapy). RESULTS: Of 1577 patients in the intention-to-treat population in the AcT trial, 368 who underwent endovascular therapy and had assessable imaging were included (179 men, median age 73 years). In multivariable analysis, mCTA-ACE score and age were independently associated with mRS ≤2 (coefficients: 0.15 and −0.05, respectively); then the age-adjusted mCTA-ACE score was derived as: mCTA-ACE score − age/3. The age-adjusted score showed superior predictive performance compared with the original mCTA-ACE score for mRS ≤2 (c-statistic 0.72 vs. 0.65, p <0.01). The c-statistics of age-adjusted and original mCTA-ACE scores for mRS ≤2 were 0.79 and 0.68, respectively (p <0.01, DeLong’s test) in the PRove-IT population who underwent endovascular therapy (n=261; 124 men, median age 73 years). CONCLUSIONS: An age-adjustment of the mCTA-ACE score may provide a more individualized prediction of functional outcomes after endovascular therapy, which helps patient selection, particularly in settings with limited access to endovascular therapy.