Apparent loss of urinary albumin during long-term frozen storage: HPLC vs immunonephelometry.

Author(s): Brinkman JW, de Zeeuw D, Lambers Heerspink HJ, Gansevoort RT, Kema IP, de Jong PE, Bakker SJ

Publication: Clin Chem, 2007, Vol. 53, Page 1520-6

PubMed ID: 17573417 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 and duration on UAC as measured by HPLC compared with detection by immunonephlometry. All specimens underwent hand inversions and were centrifuged prior to assay. Specimens with initial UAC in the 5-200 mg/L range were included in this study.

   Summary of Findings:

   When urine that had been stored at 4 degrees C for up to 5 days was evaluated, the median UAC measured by immunonephelometry was significantly lower (11 mg/L) than that measured by HPLC (55 mg/L). These measurements were used as baselines and compared to measurements taken after frozen storage. UAC decreased by an average of 21%, 28%, and 34% after storage at -20 degrees C for 4, 8, or 12 months, respectively, when measured by immunonephelometry. However, no significant changes were observed in UAC after storage of specimens at -80 degrees C for 12 months. UAC decreased by an average of 33%, 43%, and 55% after storage at -20 degrees C for 4, 8, or 12 months, respectively, when measured by HPLC. These decreases were significantly larger than the decreases measured by immunonephelometry (p<0.001 for all time points). Furthermore, an average decrease of 29% was observed in UAC after storage of specimens at -80 degrees C for 12 months when measured by HPLC (p<0.001). Variation in the stability of individual specimens was observed, particularly in the lower concentration ranges, after frozen storage. Declines in UAC were correlated with urinary pH, and urine creatinine concentrations, with smaller decreases in UAC in specimens with a higher pH and higher creatinine concentration, but the latter correlation was only true after storage at -20 degrees C for 12 months and assessment by immunophelometry.

   Biospecimens

   • Bodily Fluid - Urine

   Preservative Types

   • Frozen
   • Other Preservative

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Protein	HPLC
   Protein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage temperature	4 degrees C -20 degrees C -80 degrees C
   Storage	Storage duration	Up to 5 days 4 months 8 months 12 months
   Biospecimen Preservation	Type of fixation/preservation	Frozen Refrigeration
   HPLC Specific	Technology platform	Immunonephlometry
   Biospecimen Aliquots and Components	pH	5 6 7 8

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