Prognostic Nutritional Index (PNI) as an Independent Predictor of 3-Year Postoperative Mortality in Elderly Patients with Hip Fracture: A Post hoc Analysis of a Prospective Cohort Study

Objective: The prognostic nutritional index (PNI) has been reported as a significant predictor in various diseases. However, the prognostic value of the PNI in geriatric hip fracture patients has not been thoroughly evaluated. This study aimed to investigate the association between admission PNI and 3-year mortality in those patients. Methods: In this post hoc analysis, we included patients aged >= 65 years who underwent surgery for hip fracture between 2018 and 2019. The admission PNI was calculated as serum albumin (g/L) +5 x total lymphocyte count (x10(9)/L). Patients were categorized into four groups based on PNI quartiles (<= 43.55, 43.55-46.55, 46.55-49.20, and >49.20, respectively). The median follow-up duration was 3.1 years. Cox proportional hazards models were used to calculate the hazard ratio (HR). Receiver operating characteristic curve (ROC) was conducted for using PNI to predict mortality. Results: Of the 942 eligible patients, 190 (20.2%) patients died during the follow-up. Compared to patients in the first quartile (Q1), those in the second (Q2), third (Q3), and fourth (Q4) quartiles had significantly lower mortality risks (HRs 0.50, 95% CI 0.35-0.74; 0.41, 95% CI 0.26-0.64; and 0.26, 95% CI 0.15-0.45, respectively). The optimal cutoff of PNI for predicting mortality was set as 45.275 (sensitivity, 0.674; specificity, 0.692; area under the curve (AUC), 0.727). Patients with higher PNI (>45.275) had a significant lower mortality risk (HR 0.39, 95% CI 0.28-0.55) compared to those with lower PNI (<= 45.275). Conclusion: PNI is a reliable and independent predictor of 3-year mortality after hip fracture surgery in the elderly.