Glucose-albumin ratio (GAR) as a novel biomarker for predicting postoperative pneumonia (POP) in older adults with hip fractures

Abstract

Postoperative pneumonia (POP) is a common complication after hip fracture surgery and is associated with increased mortality and other complications in elderly patients. This study aims to evaluate biomarkers, especially the glucose-albumin ratio (GAR), for predicting POP in elderly hip fracture patients. A total of 1279 elderly patients admitted to our hospital with hip fractures were included. We assessed 29 biomarkers and focused on GAR to determine its prognostic and predictive value for POP. Multivariable logistic regression and propensity score-matched analyses were conducted to calculate adjusted odds ratios (ORs) and 95% confidence intervals (CIs) for POP, adjusting for potential confounders. Receiver operating characteristic (ROC) curves were utilized to determine the optimal cut-off of GAR for predicting POP. Among the biomarkers and combinations assessed, GAR demonstrated superior predictive capability for POP in elderly hip fracture patients. ROC analyses showed moderate predictive accuracy of GAR for POP, with an area under the curve of 0.750. Using the optimal cut-off of 0.175, the high GAR group was significantly associated with increased odds of POP (adjusted OR 2.14, 95%, CI 1.50-3.05). These associations remained significant after propensity score matching and subgroup analyses. Dose-response relationships between GAR and POP were observed. In conclusion, GAR may be a promising biomarker to predict POP risk in elderly hip fracture patients. Further studies are warranted to validate its clinical utility. However, this study has certain limitations, including its retrospective design, potential for selection bias due to the exclusion criteria, and the single-center nature of the study, which should be addressed in future prospective, multicenter studies.

Keywords: Biomarker; Glucose-albumin ratio; Hip fracture; Pneumonia; Predicting.

Figure 1

(a) Baseline data and multivariate regression analyses of each laboratory factor for POP. (b) Schematic chart for the combination of laboratory biomarkers in this study. (c) The bar graph displays the distribution of new combinations of four biomarkers between the non-POP group and the POP group.

Figure 2

ROC curves analysis to evaluate the predictive value of each combination for POP in patients with hip fractures. (a) ROC curves analysis for single laboratory factor. (b) ROC curves analysis for each new combination of four biomarkers. (c) ROC curves analysis for GAR.

Figure 3

Relationship between GAR level and POP in patients with hip fracture. (A) Predicted probabilities and the observed rate of POP; (B) Adjusted odd ratios (OR) and corresponding 95% confidence intervals (CI) are presented for each 0.05 deviation from the reference value of 0.164 mmol/L.