Association of neutrophil-to-lymphocyte ratio with age and 180-day mortality after emergency surgery

Abstract

Background: To examine the relationship between neutrophil-to-lymphocyte ratio (NLR), age, and mortality rates after emergency surgery.

Methods: In this observational study, a total of 851 patients undergoing emergency surgery between January 2022 and January 2023 were retrospective examined. Using 30 and 180 days mortality data, NLR differences and receiver operating characteristic (ROC) curves were analyzed using a 65-year threshold. A multiple logistic regression model was constructed incorporating age and NLR. Finally, Kaplan-Meier curves were constructed for mortality.

Results: Among 851 patients, the 30 and 180 days mortality rates were 5.2% and 10.8%, respectively. Median NLR in 30 days was 5.6 (3.1 to 9.6) in survivors and 8.7 (4.6 to 13.4) in deceased patients (p < 0.0001); in 180 days, it was 5.5 (3.1 to 9.8) and 8.8 (4.8 to 14.5), respectively (p < 0.0001). In the 30- and 180-days mortality analyses, median NLRs were 5.1 (2.9 to 8.9) and 4.9 (2.9 to 8.8) in survivors and 10.6 (6.9 to 16.6) and 9.3 (5.4 to 14.9) in deceased patients aged < 65 years, respectively. The ROC AUC in patients younger than 65 years was higher for 30 days (AUC 0.75; 95% CI 0.72 to 0.87) and 180 days (AUC 0.73; 95% CI 0.64 to 0.81). Multivariate logistic regression revealed that the NLR (odds ratio, 1.03 [95% CI 1.005 to 1.053; p = 0.0133) and age (odds ratio, 1.05 [95% CI 1.034 to 1.064; p < 0.0001) significantly contributed to the model. Survival analysis revealed differences in the 180 days mortality (p = 0.0006).

Conclusion: We observed differences in preoperative NLR between patients who survived and those who died after emergency surgery. Age impacts the use of NLR as a mortality risk factor.

Trial registration: NCT06549101, retrospectively registered.

Keywords: Anesthesia; Emergency surgery; Mortality; Neutrophil-to-lymphocyte ratio; Prediction; Preoperative care.

Fig. 1

A 30 days mortality analysis between survivor and deceased patients. Upper panel, neutrophil-to- lymphocyte ratio median differences: Total population (left), patients younger than 65 years (Middle) and, 65 years and above patients (Right). * 0.0302, ** p=0.0064, ns p=0.9068; Mann–Whitney U test. Lower panel, ROC curves: Total population AUC 0.60 (left), patients younger than 65 years AUC 0.75 (Middle) and, 65 years and above patients AUC 0.51 (Right). B 180 days mortality analysis between survivor and deceased patients. Upper panel, neutrophil-to- lymphocyte ratio median differences: Total population (left), patients younger than 65 years (Middle) and, 65 years and above patients (Right). **** <0.0001, *** p=0.0002, ns p=0.0991; Mann–Whitney U test. Lower panel, ROC curves: Total population AUC 0.64 (left), patients younger than 65 years AUC 0.73 (Middle) and, 65 years and above patients AUC 0.56 (Right)

Fig. 2

Receiver Operating Characteristic (ROC) Curve from Multivariate Logistic Regression between NLR and Age with Respect to Mortality. ROC curve AUC 0.75 (95% CI 0.70 to 0.80, p <0.0001)

Fig. 3

Kaplan–Meier survival and 180-day mortality analysis of NLR with a threshold of 3. Time (Days) versus estimated probability of survival (Percent). Censored point corresponds to deceased patients. No follow up lost was observed