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EDTA tubes are suitable for insulin and C-peptide measurement in resource-limited settings and can be stored at room temperature for up to 24 hours.

Author(s): Mubiru N, Mukasa R, Sekitoleko I, Balungi PA, Kakumba RM, Ongaria T, Nkabura H, Nyirenda M, Niwaha AJ, Nakanga WP

Publication: PLoS One, 2025, Vol. 20, Page e0312065

PubMed ID: 40587435 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   This study compared insulin and C-peptide levels in serum and plasma from blood stored for up to 24 h at room temperature or in a cooler box before or after centrifugation. Blood was collected from eight healthy non-fasting volunteers into syringes and transferred into twenty K₂EDTA plasma and plain serum tubes. The tubes were mixed by inversion. Half of the tubes were centrifuged at 3000 g for 10 min immediately (plasma) or after 30 min (serum) and then stored at room temperature (15-50°C) or in a cooler box (-5-15°C) for 0, 2, 6, 12 or 24 h before freezing at -20°C. The remaining specimens were stored at room temperature or in a cooler box for 0, 2, 6, 12 or 24 h before centrifugation and freezing at -20°C. Specimens were stored for 2 weeks at -20°C and then for 3 months at -80°C. Prior to analysis, specimens were thawed at room temperature for 30-60 min. C-peptide and insulin were quantified in a single batch using a Cobas 601 analyzer. Changes >10% were considered clinically significant.

   Summary of Findings:

   Plasma and serum that were centrifuged promptly and then frozen at -20°C (baseline) had similar levels of both insulin (864 pmol/L and 800 pmol/L, respectively) and C-peptide levels (17.3 μU/mL and 14.7 μU/mL, respectively). Insulin and C-peptide were more stable when specimens were stored uncentrifuged in K₂EDTA tubes than serum tubes.  Insulin and C-peptide levels remained above 90% of baseline for the full 24 h when stored centrifuged or uncentrifuged at room temperature in EDTA tubes. Insulin levels remained >90% of baseline when K₂EDTA tubes were stored in a cooler box (-5-15°C) before or after centrifugation (113% and 104%, respectively) or when serum was stored after centrifugation (97%), but decreased within 2 h when serum tubes were stored in a cooler box uncentrifuged (52%, P=0.006).  C-peptide levels were generally stable in K₂EDTA tubes regardless of centrifugation but declined to 86% of baseline within 2 h when serum tubes were stored in cooler boxes uncentrifuged and declined to 54% of baseline by 12h when serum tubes were stored at room temperature uncentrifuged.

    

   Biospecimens

   • Bodily Fluid - Blood
   • Bodily Fluid - Plasma
   • Bodily Fluid - Serum

   Preservative Types

   • Frozen

   Diagnoses:

   • Normal

   Platform:

   Analyte	Technology Platform
   Peptide	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated
   Biospecimen Aliquots and Components	Blood and blood products	Plasma Serum Whole blood
   Storage	Storage duration	0 h 2 h 6 h 12 h 24 h
   Storage	Storage temperature	Cold box (-5 to 15°C) Room temperature
   Storage	Storage conditions	Centrifuged (Plasma/Serum) Uncentrifuged (Blood)

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