Plasma neuropeptide Y in healthy children: influence of age, anaesthesia and the establishment of an age-adjusted reference interval.

Plasma concentrations of neuropeptide Y, analysed in 112 healthy children, decreased significantly with age, while sex, discomfort induced by the sampling procedure or induction of general anaesthesia did not have a significant influence. An age-adjusted upper reference limit was established and proved to be useful when tested prospectively in 56 children with tumours. Two of 18 children with preliminary diagnosis of rhabdomyosarcoma had elevated plasma neuropeptide Y; both showed malignant ectomesenchymoma (p < 0.01), a mixed tumour with neural crest features. Among 38 children with neural crest derived tumours, all 7 with benign ganglioneuromas had plasma neuropeptide Y concentrations below the reference limit, while 13 of 31 with neuroblastoma had elevated concentrations (p < 0.05). Only neuroblastoma patients with elevated plasma neuropeptide Y had a poor outcome; 10 of 13 died, whereas all with normal concentrations are alive after 3-74 months of follow-up (p < 0.001).