External Validation of the Modified Southwestern Aneurysm Severity Index in the Barrow Ruptured Aneurysm Trial Surgical Cohort

Background and objectives: Predicting functional outcomes after surgical management of ruptured aneurysms is essential. This study sought to validate the modified Southwestern Aneurysm Severity Index (mSASI), which predicts functional outcomes 1 year after treatment.

Methods: The surgical arm of a randomized controlled trial, the Barrow Ruptured Aneurysm Trial, was used to validate the mSASI model. mSASI scores incorporating the Hunt and Hess scale, Non-Neurological American Society of Anesthesiologists Physical Classification Status, imaging findings, and other modifiers were assigned and evaluated against the Glasgow Outcome Scale (GOS) score at 1 year. The model's performance was assessed for discrimination and calibration. Similar evaluations were constructed using the modified Rankin Scale (mRS) as the 1-year functional outcome measurement. Long-term outcomes (3, 6, 10 years) were also evaluated.

Results: Of 280 clinical trial patients treated surgically, 242 met the inclusion criteria. The mean age was 54.1 ± 12.9 years; 31% were men. Favorable GOS score (4-5) and mRS score (0-2) at 1 year were observed in 73.6% and 66.1% of patients, respectively. The mSASI model predicted unfavorable GOS score at 1 year with fair to good discrimination (area under the curve = 0.75, 95% CI = 0.68-0.82) and accurate calibration (R 2 = 0.98). Similar results were obtained when mRS was used as the outcome measure (area under the curve = 0.75, 95% CI = 0.68-0.82; R 2 = 0.95).

Conclusion: The mSASI model was externally validated in our cohort to predict functional outcomes using the GOS or mRS scores 1 year after surgery. This index may be used for prognosticating outcomes of patients undergoing surgery for ruptured aneurysms at short-term and long-term intervals.