Effect of freezing and thawing of serum on the immunoassay of lipoprotein(a).
Author(s): Sgoutas DS, Tuten T
Publication: Clin Chem, 1992, Vol. 38, Page 1873-7
PubMed ID: 1388112 PubMed Review Paper? No
Suggested by: ISBER
Purpose of Paper
The purpose of this paper was to determine the effects of freeze-thaw cycling and temperature, refrigerated storage, and assay on measurement of lipoprotein (Lp)(a) in serum.
Conclusion of Paper
Significant declines in Lp(a) levels were observed after freeze-thaw cycling at -20 or -70 degrees C and refrigerated storage using immunoturbidometric assay (ITA) and ELISA, but the number of cycles or days of storage to reach significance was dependent on frozen temperature and/or method of analysis. Lp(a) levels measured by ELISA were very strongly correlated with those measured by ITA, but values were lower using ELISA, and the authors attributed this to the calibrators. The authors report sodium concentrations were unaffected by freeze-thaw cycling and consequently do not contribute to changes in Lp(a).
Studies
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Study Purpose
The purpose of this study was to determine the effects of freeze-thaw cycling and freezing temperature on measurement of Lp(a) in serum by ITA and ELISA.
Summary of Findings:
When measured by ELISA, after only one freeze-thaw cycle at -20 degrees C, the mean Lp(a) declined by 15% from levels in fresh serum (p<0.05). However, when measured by ITA, the mean Lp(a) was only significantly lower after 3 or more freeze-thaw cycles at -20 degrees C compared to fresh specimens. Compared to fresh specimens, significantly lower Lp(a) levels were observed after 3 and 4 freeze-thaw cycles at -70 degrees C using ELISA and ITA, respectively (both p<0.05). The authors report that when pooled specimens were exposed to freeze-thaw cycling, no significant effects were noted after 4 freeze-thaw cycles when freezing was at -70 degrees C. Serum stored for 5 days at -20 degrees C and thawed had a similar coefficient of variance (CV) as that calculated for fresh specimens. The authors report sodium concentrations were unaffected by freeze-thaw cycling and consequently do not contribute to changes in Lp(a).
Biospecimens
Preservative Types
- Frozen
- None (Fresh)
Diagnoses:
- Normal
Platform:
Analyte Technology Platform Lipoprotein ELISA Lipoprotein Immunoturbidometric assay Electrolyte/Metal Clinical chemistry/auto analyzer Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Freeze/thaw cycling 0 cycles
1 cycle
2 cycles
3 cycles
4 cycles
Storage Storage temperature -20 degrees C
-70 degrees C
Biospecimen Preservation Type of fixation/preservation Frozen
None (fresh)
ELISA Specific Technology platform Immunoturbidmetric assay
-
Study Purpose
The purpose of this study was to determine the effects of refrigerated storage before or after freezing and assay type on the measurement of Lp(a) in serum.
Summary of Findings:
Lp(a) levels were stable in refrigerated never frozen serum for 7 and 9 days when measured by ELISA and ITA, respectively. When serum was frozen at -20 degrees C and thawed prior to refrigerated storage, Lp(a) levels were significantly lower after 2 days of storage regardless of assay method. Lp(a) levels measured by ELISA were very strongly correlated (r2=0.97) with those measured by ITA, but values were lower using ELISA, and the authors attributed this to the calibrators.
Biospecimens
Preservative Types
- Other Preservative
- None (Fresh)
- Frozen
Diagnoses:
- Normal
Platform:
Analyte Technology Platform Lipoprotein ELISA Lipoprotein Immunoturbidometric assay Pre-analytical Factors:
Classification Pre-analytical Factor Value(s) Storage Freeze/thaw cycling 0 cycles
1 cycle
Storage Storage duration 0 days
2 days
7 days
9 days
16 days
Biospecimen Preservation Type of fixation/preservation Frozen
None (fresh)
Refrigeration
ELISA Specific Technology platform Immunoturbidometric assay