DAY-TO-DAY INTRAINDIVIDUAL RELIABILITY AND INTERINDIVIDUAL DIFFERENCES IN MONOAMINES EXCRETION

The urine of 44 normal men was collected during 2 nights to evaluate c omponents of biological variation, i.e., intraindividual day-to-day va riability and interindividual variability in monoamines excretion. Mon oamines presented important interindividual variability [interindividu al coefficients of variation (%): dopamine 18.3, norepinephrine 66.7, epinephrine 85.3, normetanephrine 22.4, metanephrine 76.8, 3-methoxy-4 -hydroxyphenylglycol (MHPG) 77.0, vanilmandelic acid (VMA) 64.3, homov anilic acid (HVA) 71.3, 5-hydroxyindolacetic acid (5-HIAA) 20.4]. The reliability of these amounts was high, with intraclass correlation coe fficients ranging from 0.43 (P < 0.001) for MHPG free form to 0.65 (P < 10(-6)) for dopamine and normetanephrine (intraindividual coefficien ts of variation (%): dopamine 8.5, norepinephrine 39.9, epinephrine 45 .9, normetanephrine 10.3, metanephrine 46.3, MHPG 37.5, VMA 30.7, HVA 41.0, 5-HIAA 12.3).