Pediatric total fractionated metanephrine. Age-related reference intervals in spot urine.

Abstract

Sparse metanephrines reference intervals in pediatric populations are available and different study designs and technologies/ assays used in these studies lead to hardly transferable data from a laboratory to another. The objective of the study was to update pediatric reference intervals of total fractionated metanephrines in spot urine samples, using a commercial extraction kit run on a specific high pressure liquid chromatograph coupled with an electrochemical detector. 452 spot pediatric urinary samples previously submitted to urinalysis were consecutively included in the study with the exclusion of children's samples with diagnosis or clinical suspicion of paraganglioma/pheochromocytoma, kidney diseases and arterial hypertension. Urinary metanephrine, normetanephrine and 3-methoxytyramine were extracted with ClinRep® HPLC Complete kit and run on HPLC Prominence liquid chromatograph LC-20AT (Shimadzu Italia S.r.l. Milan, Italy) coupled with Decade II electrochemical detector (Antec Scientific, The Nederlands, provided by Alfatech S.r.l. Geneve, Italy). Results were expressed as the ratio analyteto-creatinine. Any of the three analyte required a ripartition by gender (metanephrine p=0.27; normetanephrine p= 0.90 and 3-methoxytyramine p= 0.18). A significant statistically inversely proportional relation with age was found for metanephrine (p< 0.0001; ρ= -0.72), normetanephrine (p< 0.0001; ρ= -0.75) and 3-methoxytyramine (p< 0.0001; ρ= -0.83). Reference intervals were calculated as function of age. This study provides pediatric reference intervals for urinary fractionated total metanephrines in spot urine calibrated on a specific instrumentation and extraction commercial kit.