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Decreases in albumin/creatinine and N-acetylglucosaminidase/creatinine ratios in urine samples stored at -20 degrees C.

Author(s): Manley SE, Burton ME, Fisher KE, Cull CA, Turner RC

Publication: Clin Chem, 1992, Vol. 38, Page 2294-9

PubMed ID: 1424127 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to determine the effects of storage of urine specimens at -20 degrees C on albumin, N-acetylglucosaminidase, and creatinine levels. Specimens were first assayed after up to 7 d of storage at 4 degrees C, and then again after 6 months or 2 y at -20 degrees C.

   Summary of Findings:

   Albumin and N-acetylglucosaminidase levels significantly decreased after storage at -20 degrees C for 6 months or 2 y compared to initial measurements taken in the same specimens after <7 d at 4 degrees C (p<0.001 for both analytes). Specimens with lower initial albumin concentrations showed proportionally larger decreases in albumin after frozen storage. Further, albumin and N-acetylglucosaminidase losses were greater after storage for 2 y compared to losses after 6 months of storage. Creatinine levels were slightly but significantly decreased after 6 months of storage at -20 degrees C (p<0.05), and levels were further reduced after storage for 2 y (p<0.001). Unlike albumin, reduction in creatinine levels was not dependent on initial concentration. Albumin/creatinine and N-acetylglucosaminidase/creatinine ratios were reduced after frozen storage, with greater effects on ratios initially at the lower end of the range.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Other Preservative
   • Frozen

   Diagnoses:

   • Diabetes Type 2

   Platform:

   Analyte	Technology Platform
   Protein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage duration	Up to 7 d 6 months 2 y
   Storage	Storage temperature	-20 degrees C 4 degrees C
   Biospecimen Preservation	Type of fixation/preservation	Thiomersal Frozen Refrigeration
   Clinical chemistry/auto analyzer Specific	Targeted peptide/protein	Albumin N-acetylglucosaminidase Creatinine

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