Neutrophil-to-lymphocyte ratio as a predictor of surgical site infection in acute appendicitis

Background: Surgical site infection (SSI) is one of the most common complications after appendectomy, which carries high associated morbidity. Therefore, it is essential to determine SSI predictive factors in order to prevent its occurrence. The aim of this study is to explore the role of neutrophil-to-lymphocyte ratio (NLR) as a predictor of SSI after appendectomy in children. Methods: A single-center, retrospective cohort study was performed in children who underwent appendectomy between 2017-2020. Demographics, time since symptoms onset, laboratory tests at admission, ultrasound appendiceal diameter, rate of complicated appendicitis, surgical aproach, surgery time and SSI rate were analyzed. Follow-up was performed during hospitalization and at outpatient clinic at 2 weeks and 30 days postoperatively to assess the surgical wound aspect. Diagnostic cut-off values of these markers for SSI prediction were based on the significance in the univariate analysis. Variables with a P value <0.05 in the univariate analysis were then entered into the multivariate analysis. Results: A total of 1,136 patients (710 males; 426 females) were included. SSI was reported in 53 patients (4.7%) during the 30-day follow-up after appendectomy (SSI group), with no demographic differences with the control group. Time since symptoms onset was significantly higher in SSI group (24 vs. 18 hours; P=0.034), as well as ultrasound appendiceal diameter (10.5 vs. 8.5 mm; P=0.010). Complicated appendicitis was observed in about 60% of both groups, without differences in surgical approach between them. Surgery time was statistically higher in the SSI group (62.4 vs. 47.9 min; P<0.001). SSI group presented higher counts of leukocytes, neutrophils and NLR than control group (P<0.001). NLR was the parameter with the highest AUC (AUC =0.808; P<0.001), with a cut-off point of 9.8 with maximum sensitivity (77.8%) and specificity (72.7%). NLR was an independent predictive factor for SSI in the multivariate analysis [OR 1.82 (1.13-2.73); P<0.01]. Conclusions: NLR value at admission was the most promising predictive factor for the development of SSI in children undergoing appendectomy. It is an easy, simple, inexpensive, and rapid method to detect patients at high risk for SSI. However, further prospective studies are still needed to confirm these results.