The Geriatric Nutrition Risk Index versus the Mini-Nutritional Assessment Short Form in predicting postoperative delirium and hospital length of stay among older non-cardiac surgical patients: a prospective cohort study

Backgrounds: Malnutrition has been shown to be associated with a poor prognosis in older surgical patients. Several tools are available for detecting malnutrition. But little is known about their ability to assess risks of postoperative adverse outcomes. The study aimed to compare the ability of the Geriatric Nutritional Risk Index (GNRI) and the Mini-Nutritional Assessment Short Form (MNA-SF) in predicting postoperative delirium (POD) and length of stay (LOS) among older non-cardiac surgical patients. Methods : Prospective study of 288 older non-cardiac surgical patients from the West China Hospital of Sichuan University. Preoperative nutritional status was assessed using the GNRI and MNA-SF, and patients were followed for the occurrence of POD and LOS. Multivariate logistic regression and linear regression analyses were used to identify predictors of these outcomes. The relative performance of the GNRI and MNA-SF as predictors of these outcomes were determined by Receive Operator Characteristic curves (ROC) analyses and the area under the curve (AUC). Results : Multivariate analysis revealed that high nutritional risk (GNRI < 92) and malnutrition/ risk of malnutrition (MNA-SF < 8 and MNA-SF=8-11) were significantly associated with POD. Linear regression analysis showed that low/high nutritional risk (GNRI=92-98 and GNRI < 92) and malnutrition (MNA-SF < 8) were independent predictors of prolonged LOS. Moreover, the area under the curve (AUC) of MNA-SF scores (AUC=0.718, P <0.001, 95%CI: 0.64-0.80) for POD was better than GNRI scores (AUC=0.606, P= 0.019, 95%CI: 0.52-0.69), whereas, GNRI scores (AUC=0.611, P= 0.006, 95%CI: 0.54-0.69) had larger AUC when predicting prolonged LOS as compared to MNA-SF scores (AUC=0.533, P= 0.421, 95%CI: 0.45-0.62). Conclusion : The GNRI was more effective than the MNA-SF at predicting prolonged LOS, but the MNA-SF was a superior predictor of POD in older non-cardiac surgical patients.