Effect of storage time at -20 degrees C on markers used for assessment of renal damage in children: albumin, gamma-glutamyl transpeptidase, N-acetyl-beta-D-glucosaminidase and alpha1-microglobulin.

摘要

OBJECTIVE: The objective of this study is to examine the influence of storage time at -20 degrees C on the concentration of albumin, gamma-glutamyl transpeptidase (gamma-GT), N-acetyl-beta-D-glucosaminidase (NAG), alpha(1)-microglobulin (A1M) and creatinine in a large sample of healthy children. MATERIAL AND METHODS: The New England Children's Amalgam Trial followed 534 children, aged 6-10 at baseline, for 5 years, with annual urine collections. Urine samples were analysed for creatinine, albumin, gamma-GT, NAG and A1M concentrations. Repeated measures analysis of covariance was used to model the effect of storage time on these concentrations. RESULTS: The gamma-GT concentration decreased significantly with storage time at -20 degrees C. There was also a limited decrease in NAG. Albumin, A1M and creatinine concentrations did not appear to be affected by storage time at -20 degrees C. CONCLUSIONS: If it is necessary to interpret results from samples stored for a long time at -20 degrees C, it is advisable to account for storage time in statistical models.