Normal values for pediatric urinary biochemistry in early infancy.

BACKGROUND

Urinary levels of N-acetyl-β-D-glucosaminidase (NAG), α1-microglobulin (α1-MG), and β2-microglobulin (β2-MG) are measured as markers of renal tubular damage. We previously determined normal values for these urine biochemical examinations in healthy children over 3 years old. However, the values are not applicable to children younger than 2 years old, and children less than 1 year old, in particular, seem to show very high levels for all these markers. Hence, as normal values for children below 2 years old remain unclear, we determined the normal values for urinary biochemical markers in this age group.

MATERIAL AND METHODS

Fresh urine samples were obtained from 293 healthy children (from newborns to 2-year-old children). All the samples were subjected to normal urinalysis. NAG, α1-MG, β2-MG, and creatinine (Cr) levels in extracted samples were measured immediately in the central laboratory at Kanazawa Medical Center.

RESULTS

The normal values for each biomarker in children below 2 years of age were determined. Additionally, urinary α1-MG levels were observed to decrease most rapidly with age, almost reaching the level at ≥ 3 years by 6 months after birth.

CONCLUSION

Renal tubular function can be evaluated in children < 3 years old using the normal values. Further, the most stable and useful urinary marker from early infancy seems to be urinary α1-MG.