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Considerations when measuring urinary albumin: precision, substances that may interfere, and conditions for sample storage.

Author(s): MacNeil ML, Mueller PW, Caudill SP, Steinberg KK

Publication: Clin Chem, 1991, Vol. 37, Page 2120-3

PubMed ID: 1764788 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study investigated the effects of storage temperature, centrifugation or filtration before or after storage, and vortexing before storage on levels of albumin in urine. The effect of analysis method on the coefficient of variation was also investigated. Five urine pools from healthy patients were spiked with various concentrations of albumin and two additional urine pools were preserved with tween-20 and were stored at -20˚C and assayed 20 times using each method. To investigate the effects of storage, urine from 12 patients without kidney disease were stored at -20˚C and -70˚C for 5-160 days and centrifuged, filtered, or vortexed before assay. The effect of filtration or centrifugation before storage was also investigated. Albumin levels were quantified by RIA, ELISA, and immunoturbidimetric assay.

   Summary of Findings:

   The mean degradation of specimens stored at -20˚C was 0.0192 mg/L (P=0.089) or 0.27% per day, but the mean loss was only 0.0068 mg/L for specimens stored at -70˚C. There was no effect of centrifugation, filtration, or vortexing before storage; or centrifugation or filtration after storage. The rate of albumin degradation was significantly different among individuals (P=0.0001), but effects of storage conditions on albumin degradation did not differ significantly difference among individuals. The between-day coefficients of variance were lower for RIA than ELISA or IT, regardless of preservation with Tween-20.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Other Preservative
   • None (Fresh)

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Protein	ELISA
   Protein	Radioimmunoassay
   Protein	Immunoturbidometric assay

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated Centrifuged Not centrifuged
   Biospecimen Aliquots and Components	Filtration	Filtered before storage Filtered after storage Vortexed Centrifuged before storage Centrifuged after storage
   Radioimmunoassay Specific	Technology platform	Immunoturbidimetric assay ELISA
   Storage	Storage temperature	4˚C -20˚C -70˚C
   Storage	Storage duration	5-160 days
   Biospecimen Preservation	Fixative additive/buffer	Tween20 None

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