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Preanalytical temperature and storage stability of specific IgE antibodies in serum.

Author(s): Østergaard M, Sandfeld-Paulsen B

Publication: Scand J Clin Lab Invest, 2023, Vol. 83, Page 160-165

PubMed ID: 36988143 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study compared sIgE levels among serum specimens from blood stored at room temperature in SST tubes for up to 48 h before centrifugation, serum stored at 5°C for up to 14 days, serum from blood frozen for 7 days at -20°C in collection tubes upright or inverted, serum stored for 7 days at -20°C , and serum from blood freeze-thaw cycled up to 3 times before centrifugation. Blood was collected from 10 patients with food or inhalant allergies into Vacutainer SST II Advance tubes. Unless otherwise specified, serum was isolated by centrifugation (details not provided) within 1 h and stored at 5°C until analysis (<72 h). Forty specific IgEs were quantified using immunoCAP-assays on a Phadia 1000 instrument. To investigate effects of delayed centrifugation, blood was stored at room temperature for 1, 10, 24 and 48 h before centrifugation and then stored at 5°C until analysis (<72 h). To investigate the effects of post-centrifugation storage, blood was centrifuged and stored at 5°C for 3, 7, 10 and 14 days before analysis. To investigate the effects of freezing, blood was stored in the collection tube upright or inverted and serum was stored in a secondary tube for 7 days at -20°C and thawed at room temperature before analysis. To test the effects of freeze-thaw cycling, blood was stored in the collection tube upright, thawed at room temperature on days 7 (1 cycle), 14 and 21 (2-3 cycles; an aliquot was refrozen at each time point and the remainder was centrifuged and analyzed).  The total allowable error was 1.65 times the sum of the impreci­sion and inaccuracy.

   Summary of Findings:

   A total of 37 sIgE antibodies were quantifiable, with 2-7 sIgE detected per patient. There was no effect on sIgE levels of storing blood in the collection tube for up to 48 h before centrifugation, or storing blood (upright or inverted) or serum for 7 days at -20°C. While sIgE levels were not affected by storage of serum at 5°C for up to 11 days, the upper limit of the 90% confidence interval (CI) exceeded the bias acceptance limit after 14 days, although levels were still less than the total allowable error.  While a single freeze-thaw cycle did not affect sIgE levels, the upper limit of the 90% confidence interval (CI) exceeded the bias acceptance limit after two or three cycles, and a single data point exceeded the total allowable error after three cycles.

   Biospecimens

   • Bodily Fluid - Serum
   • Bodily Fluid - Blood

   Preservative Types

   • None (Fresh)
   • Frozen

   Diagnoses:

   • Other diagnoses

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated
   Storage	Freeze/thaw cycling	0 cycles 1 cycle 2 cycles 3 cycles
   Storage	Storage conditions	Frozen upright in collection tube Frozen inverted in collection tube Frozen as serum
   Storage	Storage duration	0 h 10 h 24 h 48 h 3 days 7 days 10 days 14 days 21 days

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2. Study Purpose

   This study compared sIgE antibody levels in 24 retrospectively collected blood specimens from patients with allergies in specimens analyzed immediately with those that were stored for 4 or 8 weeks at −20°C.  All specimens were centrifuged (details not provided) within 10 h of collection, stored at room temperature for <1 week before initial analysis, and subsequently stored at -20°C. Specimens were stored for 4 or 8 weeks at −20°C upright in collection tubes (7 specimens were stored for 4 weeks and 6 specimens were stored for 8 weeks) or in either 1.5 mL SafeSeal or 3.5 mL aliquoting tubes (8 specimens were stored for 4 weeks and 3 specimens were stored 8 weeks). All tubes were thawed at room temperature for 1 h and specimens stored in the collection tube were centrifuged before analysis. Forty sIgE antibodies were quantified using immunoCAP-assays on a Phadia 1000 instrument. The acceptance limit was set at ±15% based on the UK NEQAS proficiency testing program.

   Summary of Findings:

   A total of 24 sIgE antibodies were assessed, with 1-14 tests per sample. While specimens stored for both 4 and 8 weeks at -20°C had some changes that exceeded the applied acceptance limits, the authors caution that the sample size was small. Variations in sIgE levels were similar in specimens stored at -20°C for 4 and 8 weeks.

   Biospecimens

   • Bodily Fluid - Serum

   Preservative Types

   • None (Fresh)
   • Frozen

   Diagnoses:

   • Other diagnoses

   Platform:

   Analyte	Technology Platform
   Glycoprotein	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage duration	0 weeks 4 weeks 8 weeks

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