Serum neutrophil gelatinase-associated lipocalin (NGAL) as a diagnostic tool in pediatric acute appendicitis: a prospective validation study

INTRODUCTION: NGAL has recently been studied as a biomarker in the diagnostic context of pediatric acute appendicitis (PAA), although existing series are scarce and have limited sample sizes. MATERIALS AND METHODS: A prospective observational study was designed to validate serum NGAL as a diagnostic tool in PAA. This study included 215 patients, divided into 3 groups: (1) patients undergoing major outpatient surgery (n = 63), (2) patients with non-surgical abdominal pain in whom a diagnosis of PAA was excluded (n = 53) and (3) patients with a confirmed diagnosis of PAA (n = 99). Patients in group 3 were divided into complicated or uncomplicated appendicitis. In 201 patients, a serum sample was obtained at the time of diagnosis and NGAL concentration was determined by ELISA. The Kolmogorov–Smirnov test was used to assess normality. Comparative statistical analyses were performed using the Mann–Whitney U test, the Kruskal-Wallis test and the Fisher’s exact test. To calculate the discriminative ability of the molecule, the area under the receiver-operating characteristic curves (AUC) was calculated. A p value < 0.05 established statistical significance. RESULTS: Median (interquartile range) of serum NGAL values were 38.88 (27.15–48.04) ng/mL (group 1), 51.84 (37.33–69.80) ng/mL (group 2) and 65.06 (50.50–86.60) ng/mL (group 3). The AUC (group 2 vs 3) was 0.642 (95% CI 0.542–0.741) (p < 0.001) and the best cutoff point was found to be at 40.97 ng/mL, with a sensitivity of 89% and a specificity of 34.6%. No statistically significant differences in serum NGAL values were found between patients with uncomplicated PAA and those with complicated PAA. CONCLUSIONS: This prospective validation study with a large sample size confirms that the diagnostic yield of NGAL in the context of PAA is only moderate, and therefore, it should not be used as a unique diagnostic tool. Furthermore, NGAL is not a valid biomarker to discern between uncomplicated and complicated PAA. SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1007/s00383-022-05197-w.