The Risk Analysis Index Exceeds the Modified Frailty index-5 in Predicting Worse Postoperative Outcomes in Elderly Neurosurgical Patients 80 Years and Older

Introduction: The global population of patients aged 80 years and older is the fastest-growing subgroup among elderly patients. Postoperatively, elderly neurosurgical patients may not return to baseline, due to functional decline associated with frailty. Consequently, further increasing the financial burden of care in this age group. We sought to examine the predictive threshold of two frailty risk assessment instruments (risk assessment index [RAI], and modified frailty index-5 [mFI-5]), and age for predicting mortality, extended length of stay eLOS, and prolonged length of stay (pLOS) in this age group.

Methods: The American College of Surgeons NSQIP registry was queried for patients ≥ 80 years who underwent neurosurgical intervention between 2012-2020.. Receiver operating characteristic (ROC) curve analyses were used to compare the area under the curve (AUC) RAI, mFI-5, and age for the prediction of postoperative outcomes.

Results: A total of 20710 patients were included in this study. The median age was 83 years ± 2.5 with a majority of female patients (52.7%), and white (79.8%). The RAI had a higher prediction threshold for 30-day mortality AUC 0.743 than the mFI-5 AUC 0.574 and age AUC 0.577, P< 0.001. Similar trends were seen for eLOS (RAI AUC 0.692 than the mFI-5 AUC 0.556 and age AUC 0.546, P< 0.001) and pLOS (AUC 0.665 than the mFI-5 AUC 0.523 and age AUC 0.513, P< 0.001).

Conclusion : As measured by RAI, increasing frailty was a reliable predictor of mortality, extended length of stay, and prolonged length of stay. RAI demonstrated a superior threshold of discrimination for outcomes compared to mFI-5 and age. This knowledge may help guide quality improvement initiatives in this population for the improvement of care coordination and outcomes.