Plasma ascorbic acid: measurement, stability and clinical utility revisited.

Author(s): Chung WY, Chung JK, Szeto YT, Tomlinson B, Benzie IF

Publication: Clin Biochem, 2001, Vol. 34, Page 623-7

PubMed ID: 11849621 PubMed Review Paper? No

Purpose of Paper

Conclusion of Paper

Studies

1. Study Purpose

   The purpose of this study was to compare the precision and sensitivity of HPLC and FRASC when measuring levels of ascorbic acid in heparinated plasma specimens. Plasma was stored at -70 degrees C prior to analysis.

   Summary of Findings:

   Both HPLC and FRASC showed a high level of precision and sensitivity (detection limits of 1.0 umol/L and 3.0 umol/L, respectively), with respect to ascorbic acid detection. No significant differences were found between the two detection methods when matched plasma specimens were subjected to each method on the same day.

   Biospecimens

   • Bodily Fluid - Plasma

   Preservative Types

   • Frozen

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Small molecule	HPLC
   Small molecule	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   HPLC Specific	Technology platform	FRASC

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2. Study Purpose

   The purpose of this study was to determine the most suitable anticoagulant for use when measuring ascorbic acid levels in plasma via FRASC assay. Levels were measured after storage at -70 degrees C for 0-10 days.

   Summary of Findings:

   Use of heparin as an anticoagulant resulted in stable ascorbic acid levels, even after storage for 10 days at -70 degrees C. On the other hand, after less than 30 minutes, EDTA plasma specimens had significantly lower ascorbic acid concentrations (p<0.05) when compared to paired heparinized plasma. Stability of ascorbic acid in fluoride-oxalate and citrate plasma was slightly but not significantly lower than in heparinized plasma.

   Biospecimens

   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood

   Preservative Types

   • Frozen

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Small molecule	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Storage	Storage duration	Less than 30 min 1 d 5 d 10 d
   Biospecimen Acquisition	Anticoagulant	Citrate EDTA Fluoride-oxalate Heparin

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3. Study Purpose

   The purpose of this study was to determine if exposure to artificial light, storage at different temperatures, or prolonged exposure of ascorbic acid to erythrocytes (1-24 hours) affects its stability in heparinized specimens.

   Summary of Findings:

   Exposure of chilled plasma specimens to artificial light did not result in any significant differences in ascorbic acid levels from specimens kept in the dark. Storage of heparinized blood for up to 24 hours between collection and centrifugation did not significantly affect ascorbic acid levels, indicating prolonged contact with erythrocytes has no effect. However, after storage for 24 hours at RT, ascorbic acid levels decreased by 60%. Similarly, storage for 24 h, at 4 or -20 degrees C, decreased ascorbic acid levels by 20% suggesting storage below -20 degrees C is necessary for ascorbic acid stability.

   Biospecimens

   • Bodily Fluid - Plasma
   • Bodily Fluid - Blood

   Preservative Types

   • Frozen

   Diagnoses:

   • Not specified

   Platform:

   Analyte	Technology Platform
   Small molecule	Clinical chemistry/auto analyzer

   Pre-analytical Factors:

   Classification	Pre-analytical Factor	Value(s)
   Biospecimen Acquisition	Anticoagulant	Heparin
   Storage	Storage temperature	RT 4 degrees C -20 degrees C
   Storage	Storage duration	1 h 2 h 6 h 24 h
   Storage	Storage conditions	Exposure to artificial light Storage in the dark
   Biospecimen Aliquots and Components	Blood and blood products	Whole blood Plasma
   Biospecimen Aliquots and Components	Centrifugation	Centrifugation delays investigated

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