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

BACKGROUND: 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.

METHODS: 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.

RESULTS: 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.

CONCLUSIONS: This study provides pediatric reference intervals for urinary fractionated total metanephrines in spot urine calibrated on a specific instrumentation and extraction commercial kit.