Serum lipids in Brazilian children and adolescents: determining their reference intervals

Demographic, geographic, environmental and genetic factors influence lipids. In many countries, the normal lipid ranges for laboratory tests are based on references from American children and adolescents. In this work, we determined the reference intervals (RIs) for total cholesterol (TC), high-density lipoprotein cholesterol (HDL-c), non-high-density lipoprotein cholesterol (nHDL-c), low-density lipoprotein cholesterol (LDL-c) and triglycerides (TG) in Brazilian healthy children and adolescents.

A cross-sectional study was conducted of 1,866 randomly sampled healthy children and adolescents from kindergartens and schools. Blood samples were collected after a variable period of fasting based on the age of the participant. The upper cut-off points were the 75(th) and 95(th) percentiles for TC, nHDL-c, LDL-c and TG. The 10(th) percentile (low) was used as the bottom level for HDL-c. Non-parametric tests were used for statistical analyses.

The following RI and 75(th) and 95(th) percentiles were observed for each age interval. The 95(th) percentile values obtained for TC were: 1 to 2 years, 189 mg/dL, 3 to 8 years, 199 mg/dL; 9 to 12 years, 205 mg/dL. For the nHDL c, the only age group 1 to 12 years, this percentile value was 150 mg/dL. For the LDL-cholesterol, the values corresponding to the percentiles above, aged 1 to 8 years and 9 to 12 years, were 132 mg/dL 139 mg/dL, respectively. For the triglycerides, the values corresponding to 95(th) percentile were: 1 year, 189 mg/dL; 2 to 5 years, 139 mg/dL; 6 to 12 years, 139 mg/dL . The 10(th) percentiles for HDL-c were 24 mg/dL, 28 mg/dL, 32 mg/dL and 36 mg/dL for children 1, 2, 3 and 4-12 years old, respectively.

The lipid reference intervals defined in the studied Brazilian children and adolescents differ from those recommended by the international literature and should be used for clinical decisions contributing to improve the diagnosis in this particular group in our country.