Effect of storage time at -20°C on markers used for assessment of renal damage in children: albumin, γ-glutamyl transpeptidase, N-acetyl-β-D-glucosaminidase and α1-microglobulin

Scand J Urol Nephrol. 2010 Nov;44(5):331-6. doi: 10.3109/00365599.2010.492785. Epub 2010 Jun 21.


Objective: The objective of this study is to examine the influence of storage time at -20°C on the concentration of albumin, γ-glutamyl transpeptidase (γ-GT), N-acetyl-β-D-glucosaminidase (NAG), α(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, γ-GT, NAG and A1M concentrations. Repeated measures analysis of covariance was used to model the effect of storage time on these concentrations.

Results: The γ-GT concentration decreased significantly with storage time at -20°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°C.

Conclusions: If it is necessary to interpret results from samples stored for a long time at -20°C, it is advisable to account for storage time in statistical models.

Trial registration: ClinicalTrials.gov NCT00065988.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylglucosaminidase / urine*
  • Albuminuria / urine
  • Alpha-Globulins / urine
  • Biomarkers / urine*
  • Child
  • Creatinine / urine
  • Female
  • Humans
  • Kidney Diseases / urine*
  • Male
  • Refrigeration*
  • Time Factors
  • gamma-Glutamyltransferase / urine*


  • Alpha-Globulins
  • Biomarkers
  • alpha-1-microglobulin
  • Creatinine
  • gamma-Glutamyltransferase
  • Acetylglucosaminidase

Associated data

  • ClinicalTrials.gov/NCT00065988