Lymphopaenia in the diagnosis of paediatric appendicitis: a false sense of security?

Appendicitis is a common indication for emergent surgery in children; however, it is a small proportion of presentations with abdominal pain. As viral illness is a common differential diagnosis, lymphopaenia is used by some as a predictor against appendicitis. Furthermore, neutrophil-lymphocyte ratio (NLR) has been found to predict appendicitis. We aimed to verify if lymphopaenia predicted against appendicitis in children.

Retrospective review was conducted for all patients aged 15 years and under presenting with abdominal pain to our institution in 2017, and data including age, white cell count, neutrophil and lymphocyte count, NLR, C-reactive protein and diagnosis of appendicitis were recorded. Statistical analysis was performed using Stata©. Receiver operating characteristic curves for various tests were formed and areas under curve (AUC) compared using regression, P < 0.05 was considered significant.

A total of 1263 patients were presented, of whom 546 had their blood performed and were included, 86 had appendicitis and 460 did not. Neutrophilia was the best predictor for appendicitis (AUC = 0.86), significantly higher than NLR (0.81), P < 0.05. Lymphopaenia was a poor negative predictor of appendicitis (AUC = 0.46), and while isolated lymphopaenia was more predictive (AUC = 0.23) this was inferior to the positive prediction of neutrophilia, P < 0.05.

The value of isolated lymphopaenia to predict against appendicitis is largely accounted for inherently normal neutrophils, independently lymphopaenia has little value. NLR, while predictive, is a weaker predictor than neutrophilia.