1092. External Validation of the Subarachnoid Hemorrhage International Trialists (SAHIT) Predictive Model Using the Barrow Ruptured Aneurysm Trial (BRAT) Cohort

Authors: Justin Robert Mascitelli, MD; Justin Mascitelli, MD; Tyler Cole, MD; Seungwon Yoon, BS; Peter Nakaji, MD; Felipe Albuquerque; Cameron McDougall, MD; Joseph Zabramski, MD; Michael Lawton, MD; Robert Spetzler, MD (San Antonio, TX)

Introduction: The SAHIT repository is a collection of randomized clinical trials, prospective observational studies, and hospital registries. It was used to create a predictive model of unfavorable outcome and mortality following aneurysmal SAH. The purpose is to externally validate the SAHIT model using the BRAT cohort, a trial that was not included in the SAHIT repository. Methods: This is a post-hoc analysis of the prospective, randomized BRAT. Three models were created: 1) Core (age, hypertension, WFNS grade), 2) Neuroimaging (aneurysm size/location, Fisher score), and 3) Full model (model 1 and 2 plus treatment type). The performance of the models was evaluated by measures of model discrimination (AUC) and model calibration (goodness of fit test, calibration in-the-large, and calibration slope). Results: A total of 338 patients (average age 54 years) with non-traumatic SAH from BRAT were included. The majority of patients (67.7%) had a good clinical grade. The average size of the ruptured aneurysms was 6.7 mm. The majority of aneurysms (84.1%) were located in the anterior circulation. Although patients were equally assigned to each treatment group, because a large number of crossovers, more aneurysms were clipped than coiled (67.5% vs. 32.5%, respectively). 10.1% of the patients died and 29.6% experienced an unfavorable outcome. For unfavorable outcome, the AUCs for the three models were: 0.728, 0.732, and 0.734, respectively. For mortality, the AUCs for the three models were: 0.721, 0.739, and 0.744, respectively. Overall, all models showed good calibration, and the measures of calibration fell within those produced in the SAHIT study. The AUCs generated were within the 95% CI values in the SAHIT model. Conclusion: Using the BRAT data, we have externally validated the SAHIT model for predicting unfavorable outcome and mortality after SAH. The model may be used to counsel patients and families on prognosis following aneurysmal SAH.