Reference values of IGF-I in children from birth to 5 years of age, in Burkina Faso, using blood samples on filter paper

Abstract

Objectives The aims of this study were to validate the use of filter paper to measure insulin-like growth factor-I (IGF-I) and to establish normal levels of IGF-I in children appearing healthy, from birth to 5 years of age in an African population. Methods We determined IGF-I from blood collected on filter paper. We validated this method by comparing the IGF-I values from dried blood spots on filter paper (kept at 4 °C and ambient temperature) and from serum among 13 children under 5. IGF-I were measured by the classical IGF-I RIA, after separation of the IGF-I from its binding proteins, using Sep-Pak chromatography. To establish normal levels of IGF-I, we conducted a cross-sectional study and collected blood samples with filter paper among 360 children in Ouagadougou (Burkina Faso). Results IGF-I determined from dried blood spots on filter paper were in good agreement with IGF-I levels obtained from blood serum, whether the filter papers were kept at 4 °C or at ambient temperature. The results of IGF-I-levels in apparently healthy children showed that geometric mean IGF-I ranged from 27 μg/l in boys younger than five months to 31 μg/l in 5-year-old boys. In girls, mean IGF-I ranged from 29 μg/l for girls younger than five months to 45 μg/l at the age of 5. From birth to 24 months, IGF-I decreased by 0.32 ± 0.08 μg/l/month in boys and by 0.27 ± 0.06 μg/l/month in girls and these decreases were not significantly different ( p = 0.95). After the age of 24 months, there was an increase in IGF-I of 4.9 ± 1.3 μg/l/year in boys and of 8.4 ± 0.8 μg/l/year in girls. This increase was indeed significantly different ( p < 0.001). Conclusions Reference values of IGF-I for African boys and girls were determined. They will be used for endocrine evaluations and nutritional monitoring.