Immunoreactive renin concentrations in healthy children from birth to adolescence

We establish normative data for immunoreactive renin concentration in serum of healthy children. In a retrospective study, surplus sera of 281 healthy children, aged 0-18 years, were collected from the laboratory. The determinations were performed with a commercially available two-site immunoradiometric assay. Functional sensitivity was 4.0 mU/l, inter-assay and intraassay variance were 7.0-18.3% and 3.8-7.5%, respectively. In umbilical cord and during the first 4 days of life, renin concentrations (geometric mean) were significantly higher (P < 0.05) than in older infants and children [umbilical cord: 155.2 mU/l; newborn infants (2-4 days of life): 90.9; newborn infants (5-7 days of life): 32.5; 2 weeks-3 months: 40.8; 4 months-1 year: 54.5; 1-3 years: 46.3; 3-5 years: 48.5; 5-7 years: 51.6; 7-11 years: 38.5; 11-15 years: 37.7; 15-18 years: 31.9], Newborn infants delivered by Caesarian section had significantly lower renin concentrations in umbilical cord than those delivered vaginally (P < 0.02). Considering the methodological advantages and disadvantages of plasma renin activity and renin concentration assays, renin measurement was at least as valuable and accurate as plasma renin activity determination. (C) 1998 Elsevier Science B.V. All rights reserved.