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Evaporation of serum after long-term biobank storage: A chemical analysis of maternal serum from a large Danish pregnancy screening registry.

Author(s): Uldbjerg CS, Sørensen KM, Lindh CH, Rantakokko P, Hauser R, Juul A, Andersson AM, Bräuner EV

Publication: PLoS One, 2023, Vol. 18, Page e0293527

PubMed ID: 37883412 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This paper compared the concentration of Na+ and Cl- in serum specimens that were stored at -20°C for 27-37 years in order to assess effects associated with evaporation. The number of specimens with Na+ or Cl- levels that were outside of the normal reference range were compared between serum collection from pregnant women that was stored frozen for 27-37 years and serum collected from non-pregnant women that was analyzed fresh.  This study used serum that was retrospectively collected from 275 pregnant women (14-22 weeks of gestation) between 1985 and 1995 (25 patients/per year). Serum was obtained from coagulated blood by centrifugation at 4°C and 3000 g (duration not specified) and stored at -20°C in screw top cryotubes for 27-37 years before analysis. Serum was thawed at room temperature for ≤2 h and mixed before quantification of Na and Ca using a Roche Cobas 6000 ion-selective electrode. Na+ and Cl- levels were compared to those in serum that was collected from 24,199 non-pregnant women; serum specimens were obtained by centrifugation at 3100 RPM for 10 min at 21˚C and stored for <24 hours in a climate chamber before analysis.

   Summary of Findings:

   A high percentage of serum specimens collected from pregnant women had Na+ or Cl- concentrations that were outside of the normal range (38.9% and 43.6%, respectively), with the vast majority of specimens in question above the normal range (106 of 107 for Na+ and 116 of 120 for Cl-). In contrast, only 3.7% and 4.3% of specimens fell outside the normal range for Na+ and Cl-, respectively, when serum from non-pregnant women were analyzed within 24 h of collection; the majority of these specimens fell below the normal range for Na+ and Cl-.  , The variability in Na+ and Cl- was higher than the normal biological variation for all of the frozen storage durations evaluated using serum collected from pregnant women. Importantly, the Na+ and Cl- concentrations in serum from pregnant women were not correlated with frozen storage duration, and no consistent effect of specimen volume was observed.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • None (Fresh)
   • Frozen

   Diagnoses:

   • Not specified
   • Pregnant

   Platform:

   Analyte	Technology Platform
   Electrolyte/Metal	Ion selective electrode

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Preaquisition	Diagnosis/ patient condition	Pregnant Non-pregnant
   Storage	Storage duration	27-37 years
   Biospecimen Aliquots and Components	Aliquot size/volume	Unspecified range of volumes < 2 mL

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