Effect of freeze/thaw cycles on several biomarkers in urine from patients with kidney disease.
Author(s): Zhang Y, Luo Y, Lu H, Wang N, Shen Y, Chen R, Fang P, Yu H, Wang C, Jia W
Publication: Biopreserv Biobank, 2015, Vol. 13, Page 144-6
PubMed ID: 25880475 PubMed Review Paper? No
Purpose of Paper
The purpose of this paper was to determine the effects of freezing and thawing method, frozen storage temperature and the number of freeze-thaw cycles on the measurement of total protein, calcium, albumin, and potassium in urine.
Conclusion of Paper
In general, analytes were more stable when urine was directly frozen than when frozen by temperature gradient and when frozen at -80°C rather than at -20°C. When directly frozen at -80°C, a significant decline in total protein and albumin levels from those in fresh specimens was noted after 6 freeze-thaw cycles, but calcium and potassium levels remained comparable to those in fresh specimens, even after 6 freeze-thaw cycles.
Studies
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Study Purpose
The purpose of this study was to determine the effects of freezing and thawing by gradient rather than directly, frozen storage temperature and the number of freeze-thaw cycles on the measurement of total protein, calcium, albumin, and potassium in urine. 24 h urine specimens from 11 patients with various forms of kidney disease, including diabetic nephropathy, were centrifuged, assayed once, aliquoted and frozen at -80°C and -20°C. The authors state that specimens were frozen and thawed directly or by gradient but the methods used for each were not specified.
Summary of Findings:
The authors report comparable results between the two different directly thawed and gradient-thawed specimens, but more significant effects of freeze-thaw cycling were observed when specimens were gradually frozen than directly frozen. Compared to fresh specimens, total protein levels declined after 6 freeze-thaw cycles at -20°C, regardless of freezing method, but when specimens were frozen at -80°C, this decline was observed after 6 cycles in directly frozen and 4 cycles in gradually frozen urine. Albumin levels declined from levels in fresh specimens after 3 cycles at -20°C or 6 cycles at -80°C, regardless of freezing method. While calcium levels were comparable after 6 freeze-thaw cycles at -80°C to those in fresh specimens, levels were slightly lower after 6 cycles at -20°C than in fresh specimens, regardless of freezing method. Potassium levels were comparable to those in fresh specimens after 6 freeze-thaw cycles at -80°C or when directly frozen for 6 cycles at -20°C, but they were lower than in fresh specimens after 6 cycles at -20°C when frozen gradually.
Biospecimens
Preservative Types
- Frozen
- None (Fresh)
Diagnoses:
- Other diagnoses
- Diabetes Type 2
Platform:
Analyte Technology Platform Protein Colorimetric assay Electrolyte/Metal Ion selective electrode Electrolyte/Metal Clinical chemistry/auto analyzer Protein Clinical chemistry/auto analyzer Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Biospecimen Preservation Type of fixation/preservation Frozen
None (fresh)
Biospecimen Preservation Cooling or freezing method/ rate Cooling device
Direct transfer to freezer
Storage Storage temperature -20°C
-80°C
Storage Freeze/thaw cycling 0 cycles
1 cycle
2 cycles
3 cycles
4 cycles
5 cycles
6 cycles
Storage Thaw temperature/condition Directly
Temperature gradient