Effect of storage at 4 degrees C and -20 degrees C on lipid, lipoprotein, and apolipoprotein concentrations.

Author(s): Evans K, Mitcheson J, Laker MF

Publication: Clin Chem, 1995, Vol. 41, Page 392-6

PubMed ID: 7882514 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 storing unfractionated serum at either 4 degrees C or -20 degrees C for up to 3 months on lipid, lipoprotein, and apolipoprotein concentrations. Serum was obtained from 42 individuals with a range of lipid values, both above and below the standard cutoffs of healthy levels.

   Summary of Findings:

   While total cholesterol and triglyceride, and apolipoprotein A-I (apoA-I) concentrations were not significantly affected by any of the tested storage conditions, apolipoprotein B (apoB) concentration increased by 5.3% (p<0.001) after being stored for 3 months at -20 degrees C. Storage for 10 days at 4 degrees C resulted in an increase in very-low-density lipoprotein (VLDL) esterified cholesterol, and both low-density lipoprotein (LDL) and high-density lipoprotein (HDL) triglycerides. Under the same storage conditions, LDL and HDL free cholesterol levels and HDL phospholipid concentrations decreased. When unfractionated serum was stored for 10 days at -20 degrees C, VLDL triglyceride and phospholipid concentrations increased along with LDL free cholesterol concentrations, while HDL triglyceride and phospholipid concentrations decreased. Finally, 3 months storage at -20 degrees C resulted in increases in VLDL free cholesterol and phospholipid concentrations, all intermediate-density lipoprotein (IDL) analytes, and LDL triglycerides. At the same time, these storage conditions caused decreases in VLDL triglyceride and protein concentrations, and all HDL analytes. LDL appeared to be the most stable fraction, and decreases observed in the HDL fraction after storage for 3 months at -20 degrees C were not compensated by increases in the other fractions suggesting more than mere redistribution of lipids.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • Other Preservative
   • Frozen

   Diagnoses:

   • Normal
   • Other diagnoses

   Platform:

   Analyte	Technology Platform
   Lipid	Clinical chemistry/auto analyzer
   Lipoprotein	Clinical chemistry/auto analyzer
   Protein	Clinical chemistry/auto analyzer
   Steroid	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Preservation	Type of fixation/preservation	Preservative cocktail Frozen Refrigeration
   Preaquisition	Diagnosis/ patient condition	High cholesterol High triglycerides
   Storage	Storage duration	<3 d 10 d 3 months
   Storage	Storage temperature	4 degrees C -20 degrees C

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