Reference ranges of serum bile acids in children and adolescents

Background: Bile acids (BA) are found predominantly in bile but also in serum, where they can be used as markers for inborn and acquired hepatobiliary disorders. We measured serum BA levels by mass spectrometry to determine reference ranges for healthy children and adolescents in different age groups. Methods: In 194 healthy children and adolescents (0-19 years) concentrations of serum BA and BA composition were determined using high-performance liquid chromatography high-resolution mass spectrometry. Individuals were classified by ages into five groups: 0-5 months, 6-24 months, 3-5 years, 6-11 years, and >11 years. Results: The 95% confidence interval of serum total BA values in newborns was 3.85-6.32 mu mol/L. In the cohort aged 6-24 months total BA values were significantly higher (6.61-9.43 mu mol/L; p<0.001). During growth, values decreased (6-11 years; 3.61-5.41 mu mol/L), and after 11 years (3.09-4.12 mu mol/L) resembled those in adults (0.28-6.50 mu mol/L). With respect to conjugation patterns, in neonates BA were primarily conjugated with taurine; however, after 6 months glycine conjugates clearly predominated. Conclusions: Our data show that serum BA values vary substantially during the first years of life and that reference ranges for BA are age-dependent. The physiologic mechanisms underlying these variations remain to be determined.