A Retrospective Cohort Study to Evaluate Adding Biomarkers to the Risk Analysis Index of Frailty

Introduction: The Risk Analysis Index (RAI) is a frailty assessment tool associated with adverse postoperative outcomes including 180 and 365-d mortality. However, the RAI has been criticized for only containing subjective inputs rather than including more objective components such as biomarkers. Methods: We conducted a retrospective cohort study to assess the benefit of adding common biomarkers to the RAI using the Veterans Affairs Surgical Quality Improvement Program (VASQIP) database. RAI plus body mass index (BMI), creatinine, hematocrit, and albumin were evaluated as individual and composite variables on 180-d postoperative mortality. Results: Among 480,731 noncardiac cases in VASQIP from 2010 to 2014, 324,320 (67%) met our inclusion criteria. Frail patients (RAI >= 30) made up to 13.0% of the sample. RAI demonstrated strong discrimination for 180-d mortality (c = 0.839 [0.836-0.843]). Discrimination significantly improved with the addition of Hematocrit (c = 0.862 [0.859-0.865]) and albumin (c = 0.870 [0.866-0.873]), but not for body mass index (BMI) or creatinine. However, calibration plots demonstrate that the improvement was primarily at high RAI values where the model overpredicts observed mortality. Conclusions: While RAI's ability to predict the risk of 180-d postoperative mortality improves with the addition of certain biomarkers, this only observed in patients classified as very frail (RAI >49). Because very frail patients have significantly elevated observed and predicted mortality, the improved discrimination is likely of limited clinical utility for a frailty screening tool.