Storage temperature and differing methods of sample preparation in the measurement of urinary albumin.

Author(s): Collins AC, Sethi M, MacDonald FA, Brown D, Viberti GC

Publication: Diabetologia, 1993, Vol. 36, Page 993-7

PubMed ID: 8243884 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 temperature, duration, and container, freeze-thaw cycling, and centrifugation on albumin concentrations in nitrate negative urine specimens collected from normal and diabetic patients with a range of starting concentrations. All specimens were vortexed prior to assaying, and where indicated, some were also centrifuged, and supernatant was assayed.

   Summary of Findings:

   Storage of urine at 4 or 20 degrees C for up to 1 week had no significant effects on urinary albumin concentrations compared to measurements taken within 24 or 48 h after collection and storage at 4 degrees C. Frozen storage of urine at -20 or -40 degrees C for up to 6 months also had no effects on albumin concentrations. Up to 6 freeze-thaw cycles in a 6 week period had no effect on urinary albumin concentrations in specimens from healthy individuals or diabetic patients, regardless of initial levels. No differences were observed between albumin measurements taken with or without centrifugation of specimens prior to assaying. Type of storage container had no significant effect on urinary albumin concentrations when specimens were stored for 1 week or 1 month at -20 degrees C. However, small but insignificant decreases in albumin concentrations (about 7%) were observed, for all storage tube types and all baseline concentration ranges, after 1 month of storage at -20 degrees C compared to measurements taken within 24 or 48 h after collection and storage at 4 degrees C. The addition of gelatine to the storage tubes attenuated the observed decreases (about 4%). The insignificant nature of this decrease and the fact that no such decrease was seen after frozen storage at -20 degrees C for up to 6 months in the experiment previously mentioned suggests this is likely clinically irrelevant.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • None (Fresh)
   • Other Preservative
   • Frozen

   Diagnoses:

   • Diabetes Type 1
   • Diabetes Type 2
   • Normal

   Platform:

   Analyte	Technology Platform
   Protein	Radioimmunoassay
   Protein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	Frozen None (fresh) Refrigeration
   Preaquisition	Biomarker level	Normoalbuminuric (<20 mg/L) Microalbuminuric (20-300 mg/L) Proteinuric (>300 mg/L)
   Storage	Storage temperature	20 degrees C 4 degrees C -20 degrees C -40 degrees C
   Storage	Storage duration	0 d Less than 24 h 1 d Less than 48 h 2 d 7 d 2 weeks 3 weeks 4 weeks 5 weeks 6 weeks 1 month 6 months
   Storage	Freeze/thaw cycling	0 cycles 1 cycle 2 cycles 3 cycles 4 cycles 5 cycles 6 cycles
   Storage	Type of storage container	Polypropylene tubes Polystyrene tubes Borosilicate glass tubes
   Biospecimen Preservation	Fixative additive/buffer	Gelatine in phosphate buffered saline None
   Biospecimen Aliquots and Components	Centrifugation	Centrifuged Not centrifuged

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