“…Moreover, muscular mass, disease state, and drugs further alter creatinine excretion. For instance, the compilation of four recently published reference intervals and our own data using HPLC with electrochemical detection for NE, DA, VMA, and HVA in children <1 year of age illustrates this variability indicating upper reference limits at respectively <75, 73, 130, 140 and 280 nmol/mmol creatinine for NE; at 1104, 1428, 1500, 1500 and 1600 nmol/mmol creatinine for DA; at 10, 12, 14, 14 and 30 mmol/mmol creatinine for VMA; at 20, 20, 20, 23 and 32 mmol/mmol creatinine for HVA [8,9,22,23]. The high sensitivity of plasma free metanephrines observed in our work, which has also been established for the diagnosis of pheochromocytoma, may be attributed to the expression of catechol-O-methyl transferase by neuroblastoma.…”