Falsely low urinary albumin concentrations after prolonged frozen storage of urine samples.

Author(s): Brinkman JW, de Zeeuw D, Duker JJ, Gansevoort RT, Kema IP, Hillege HL, de Jong PE, Bakker SJ

Publication: Clin Chem, 2005, Vol. 51, Page 2181-3

PubMed ID: 16244297 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 and mixing on UAC in specimens with initial UACs in the normo- and microalbuminuric ranges. All specimens were collected and held at 7 degrees C until freezing or analysis. Specimens that were frozen at -20 degrees C were thawed at 7 degrees C for 1-3 days prior to analysis.

   Summary of Findings:

   Specimens that were not mixed after frozen storage for 3-5 months showed significant decreases (-28.6%) in UAC compared to baseline values measured in aliquots held at 7 degrees C (p<0.001). Specimens that were mixed by either vortex or hand inversion after 3-5 months of frozen storage did not show significant changes in UAC. However, specimens that were frozen for 18-24 months and mixed prior to analysis showed significant decreases in UAC after both hand inversions (-26.2%) and vortexing (-24.7%) (p<0.001 for both), but no significant differences between mixing methods were observed, regardless of storage duration or UAC concentration category. Specimens with high UACs (200-500 mg/L) showed a significantly attenuated decrease in UAC after frozen storage compared to specimens falling in the lower UAC categories (p<0.001), and this was true regardless of duration of storage.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Frozen
   • Other Preservative

   Diagnoses:

   • Normal
   • Other diagnoses

   Platform:

   Analyte	Technology Platform
   Protein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Preaquisition	Diagnosis/ patient condition	Microalbuminuria
   Storage	Storage temperature	7 degrees C -20 degrees C
   Storage	Storage duration	3-5 months 5-8 months 8-12 months 12-18 months 18-24 months
   Biospecimen Preservation	Type of fixation/preservation	Frozen Refrigeration
   Biospecimen Aliquots and Components	Biospecimen mixing	None Hand inversion Vortexing
   Preaquisition	Biomarker level	0-10 mg/L UAC 10-20 mg/L UAC 20-40 mg/L UAC 40-80 mg/L UAC 80-200 mg/L UAC 200-500 mg/L UAC

   View more