[Neutrophil-to-lymphocyte ratio as a predictor of peritonitis in acute appendicitis in children]

The neutrophil-to-lymphocyte ratio (NLR) has been postulated as an inflammatory marker in several abdominal pathologies such as acute appendicitis (AA). However, there are few studies that determine its association with the degree of severity of AA. This is the first study that analyzes the usefulness of NLR as a predictor of peritonitis in children with AA.

Retrospective observational study in patients treated of AA during the years 2017 and 2018. They were divided into two groups according to the intraoperative diagnosis (uncomplicated AA and AA with peritonitis). Demographic and analytical variables were analyzed. The NLR was defined as the quotient between the absolute values of neutrophils and lymphocytes. The sensitivity and specificity for the diagnosis of peritonitis of different analytical parameters were determined by ROC curves.

A total of 398 patients were included (uncomplicated AA n=342 and AA with peritonitis n=56), with a mean age of 10.5±2.9 years. The NLR had an area under the curve (AUC) of 0.78, significantly higher than the determination of leukocytes (AUC 0.71, p=0.002) and of neutrophils (AUC 0.74, p=0.009). No differences were observed when compared to the determination of C-reactive protein (AUC 0.79, p=0.598). A cut-off point of NLR>8.75 was estimated with a sensitivity and specificity of 75.0 and 72.2% respectively.

The NLR is a useful tool to predict the presence of peritonitis in AA, and could be considered an alternative to other higher cost determinations such as C-reactive protein.