Reference serum creatinine levels according to sex, age, and height in children with Down syndrome.

Standard serum creatinine (S-Cr) levels in healthy children fluctuate with age and sex. However, it is unclear if this fluctuation in S-Cr levels is present for children with Down syndrome (DS) who show atypical growth rate. Therefore, we aimed to establish specific reference S-Cr levels for DS and compare them with the prevailing standard levels. We retrospectively reviewed 984 children with DS aged 3 months to 18 years who visited our medical center. Patients with diseases affecting S-Cr levels were excluded. We calculated the reference S-Cr levels according to sex, age, and length/height using medical records. A total of 3765 examinations of 568 children with DS were registered for this study. Ages and S-Cr levels were examined for boys (y = 0.032x + 0.20; r = 0.868, P < 0.0001), and girls (y = 0.024x + 0.23; r = 0.835, P < 0.0001). S-Cr levels in children aged >9 years were significantly higher in boys than in girls. The 430 children with DS aged 2-8 years were examined 1867 times. Height and S-Cr levels showed a significantly strong positive correlation (r = 0.670, P < 0.001) with regression equation y = 0.37x. The quintic equations calculated with S-Cr levels and length/height for boys (336 children, 2043 tests, r = 0.887) and girls (232 children, 1722 tests, r = 0.805) werey =  - 6.132x + 32.78x - 67.86x + 68.31x - 33.14x + 6.41, and y = 0.09542x + 1.295x - 6.401x + 10.35x - 6.746x + 1.772. All calculated results varied from the standard levels for healthy children.Conclusion: This study established reference S-Cr levels and quintic equations specific for children with DS. These reference levels would be potentially useful in evaluating S-Cr levels and renal function in this population. What is Known: •Standard serum creatinine levels vary with age and sex to reflect muscle mass. •Reference serum creatinine levels specific to children with Down syndrome who show growth rates different from those of healthy children have not been established. What is New: •Serum creatinine levels in children with Down syndrome showed different trajectories for sex, age, and length/height when compared with the standard levels for healthy children. •This report on specific reference serum creatinine levels for children with Down syndrome is useful in the assessment of renal function in these children.