Values for urinary β-microglobulin and N-acetyl-β-D-glucosaminidase in normal healthy infants

Abstract Background : Measuring urinary β₂ microglobin (B2M) and N -acetyl-β-D-glucosaminidase (NAG) excretion is widely used as a valuable clinical tool in assessing renal tubular lesions. However, few data are available on normal values for urinary excretion of B2M and NAG in infancy.
Methods : Urinary B2M and NAG were measured in healthy infants. The logarithmic values of urinary B2M, NAG. B2M/creatinine ratio and NAG/creatinine ratio were distributed almost normally and reference ranges were calculated from the logarithms of the observed values.
Results : The levels of urinary B2M and B2M/creatinine ratio were highest in the 1-month-old group, followed by a decrease during the first 3 months. Urinary B2M excretions in the 3-monfh-old group showed rather lower levels than those of the 12-month-old and 36-month-old groups. Although urinary NAG excretions were almost constant throughout all groups, urinary NAG/creatinine ratio decreased gradually until 3 years of age.
Conclusions : We suggest that these reference ranges are of importance in evaluating tubular damage due to a variety of renal diseases in infancy.