Urinary excretion of retinol-binding protein in healthy children and adolescents.

Retinol-binding protein (RBP) is a marker of tubular reabsorption in the kidneys. The aim of our study was to investigate urinary RBP excretion in healthy children to obtain reference values related to age and pubertal stage. Overnight samples from 143 subjects (73 girls, 70 boys) aged 10-18 years were investigated. RBP was quantified by a solid-phase sandwich enzyme immunoassay. Both the RBP excretion rate and the RBP/creatinine ratio (RBP/Cr) showed a skewed distribution. The medians and the 5th-95th percentiles were 38 ng/min (15-127) and 9 micrograms/mmol (4-23), respectively. The RBP excretion rate and RBP/Cr ratio were similar in both sexes, and linear multiple regression analysis showed no association with age or pubertal stage, although a weak relationship (r = 0.27) was found between RBP excretion rate and age in boys and RBP/Cr ratio and age (r = -0.28) in girls by simple correlation analysis. The correlation between RBP excretion rate and RBP/Cr ratio was 0.76; the RBP excretion rate and RBP/Cr ratio measured on 2 consecutive days, showed a correlation coefficient of 0.84 and 0.88, respectively. We conclude that overnight RBP excretion in children over 10 years shows a low day-to-day variation and, in practical terms, is independent of age, gender and pubertal stage.

Urinary albumin excretion rate and puberty in non-diabetic children and adolescents.

Slightly elevated urinary albumin excretion rate (microalbuminuria) is a marker of early diabetic nephropathy, but it is unclear if the established definition of microalbuminuria (20-200 micrograms/min) is correct for children and adolescents. We investigated the albumin excretion rate, albumin/creatinine ratio and urinary albumin concentration in 150 healthy schoolchildren and adolescents to (a) obtain a reference value for albumin excretion rate, (b) relate albumin excretion to pubertal stages and (c) evaluate albumin/creatinine ratio and morning albumin concentration as screening methods for elevated albumin excretion rate. Albumin concentration was measured by immunoturbidimetry in timed overnight urine samples. The albumin excretion showed a skewed distribution (geometric mean 3.2 micrograms/min, 95 percentile 15.1 micrograms/min). In girls, a peak in the albumin excretion rate was found at the pubertal stage 4 (Tanner) and in boys at stage 5. Albumin/creatinine ratio of 2.5 mg/mmol as a screening level for elevated albumin excretion (15 micrograms/min) showed a high positive (0.88) and negative (0.99) predictive value.

Meningococcal phenotypic and genotypic characteristics and human antibody levels.

During a 2-month period in 1984, throat and blood samples were collected from 1,102 healthy persons of different ages living in the city of Tromsø, Norway. One hundred and eight persons (9.8%) were meningococcal carriers, but the carrier rate varied with sex and age. Twenty-nine isolates (26.9%) were of serogroup B, and 31 (28.7%) isolates contained the serotype 15 antigen. Sixty-eight (63.0%) isolates were nontypable, 49 (45.4%) were nongroupable, and 21 (19.4%) were sulfonamide resistant. All nine serotype 2a isolates and eight (25.8%) of the serotype 15 isolates were sulfonamide resistant. Only these eight serotype 15, sulfonamide-resistant isolates had a DNA fingerprint similar to that of the majority of systemic isolates of Neisseria meningitidis in Norway. The average level of antimeningococcal immunoglobulin G antibodies, as determined by a whole-bacterium enzyme immunoassay with a systemic B:15 meningococcal strain as the antigen, was low until 12 to 15 years of age and then steadily increased.