URINARY PORPHYRIN EXCRETION IN NORMAL-CHILDREN AND ADULTS

The relationship of random urinary porphyrin and creatinine values as functions of age and sex was examined in a normal population. Total urinary porphyrin was measured by a solvent extraction technique, while urinary creatinine was evaluated by an alkaline picrate method. Random urine specimens from 120 healthy patients (81 children and 39 adults) were evaluated. In both pediatric and adult populations, a strong correlation was found between urinary concentrations of porphyrin and creatinine (r = 0.7, P < 0.0001). Urinary porphyrin excretion in gmol/mol creatinine (µg/g) was inversely related to both age (r = -0.59, P < 0.0001) and weight (r = -0.61, P < 0.0001) until approximately 9 years of age or 30 kg. Urinary porphyrin excretion in children 9 to 18 years of age was lower than that of younger children (P < 0.0001) and approached adult values. Sex was not found to be a factor until 9 to 18 years of age, when females had higher urinary creatinine concentrations (P < 0.05), but lower urinary porphyrin excretions (P < 0.05) than similarly aged males. The converse was observed when similar values of adult women were compared with those of adult men. Men also had higher urinary porphyrin concentrations than women (P < 0.01). Men had increased urinary creatinine concentration (P < 0.05) and decreased porphyrin excretion ratios (P < 0.05) when compared with males 9 to 18 years of age. Women had significantly lower urinary creatinine (P < 0.001) and porphyrin (P < 0.001) concentrations than females 9 to 18 years of age. Quantitative analysis of porphyrin and creatinine concentrations in random urinary specimens can provide diagnostically informative assessments of porphyrinuria, although effects of age, weight, and sex and of diurnal variation of porphyrin excretion must be considered. © 1991, National Kidney Foundation, Inc.. All rights reserved.