No reliably specific marker for complicated appendicitis has been identified. The ratio of serum C-reactive protein (CRP) to albumin (ALB) (CRP/ALB ratio) is a new inflammation-based prognostic score that is associated with the severity of inflammation. The aim of this study was to evaluate the predictive value of CRP/ALB ratio for the diagnosis of complicated appendicitis in children.

A retrospective study of 296 children with acute appendicitis was conducted with assessments of demographic data, clinical symptoms, pre-operative laboratory results, abdominal ultrasound examinations and clinical outcomes. According to the postoperative pathological results, patients were divided into a simple appendicitis group (169 patients) and a complicated appendicitis group (127 patients). SPSS version 22.0 was used to analyse the data.

Of the 296 patients, CRP/ALB ratio was higher in complicated appendicitis than in simple appendicitis (P < 0.05). Logistic regression analysis showed that higher levels of white blood cell count (WBC), CRP, CRP/ALB ratio, and increased incidence in submucosal layer loss and appendicolith were independent risk factors for complicated appendicitis in children. Receiver operating characteristic curve analysis showed that the area under the curve of the CRP/ALB ratio (0.883) was larger than that of WBC (0.702), CRP (0.802), ALB (0.835), submucosal layer loss (0.633) and appendicolith (0.673). A CRP/ALB ratio ≥ 1.39 was found to be a significant marker in the prediction of complicated appendicitis, with 86.61% sensitivity and 84.62% specificity. Patients with a CRP/ALB ratio ≥ 1.39 had a 31.263 times higher chance of having complicated appendicitis (95% CI: 16.449–59.418) than those with a CRP/ALB ratio < 1.39.

The admission CRP/ALB ratio was significantly higher in children with complicated appendicitis. The CRP/ALB ratio is a novel but promising haematological marker that aids in the differentiation of acute complicated and simple appendicitis.