Lessons from the NIST micronutrients quality assurance program for vitamin C, 1993 to 2015: sample stability, assay reproducibility, and use of controls to improve comparability.
Anal Bioanal Chem
; 413(2): 289-298, 2021 Jan.
Article
in En
| MEDLINE
| ID: mdl-33140124
ABSTRACT
Vitamin C is a necessary micronutrient that is involved in many biological processes. In preserved human plasma and serum, vitamin C is most meaningfully analyzed as total ascorbic acid (TAA). From 1993 through 2015, the National Institute of Standards and Technology (NIST) coordinated 40 interlaboratory studies (ILS) devoted to improving the between-participant comparability of TAA measurements. The results from these ILS demonstrate that the concentration of TAA ([TAA]) is stable for at least 20 years in serum diluted 1 + 1 (volume fraction) with 10% mass concentration aqueous metaphosphoric acid (MPA) and stored at -80 °C. The between-participant relative reproducibility precision, expressed as a coefficient of variation (CV), improved from over 16% to under 9% over the course of the studies. Normalization of test samples (i.e., ex post-facto recalibrating the as-submitted results) using participant-prepared serum-free calibration solutions did not improve reproducibility. Normalization to one control sample having a similar serum-based matrix as the test samples improved the CV to 7%; normalization to two such controls reduced the CV to 4%. Multicenter studies that require the highest degree of measurement comparability among the participants should consider calibrating with materials that have a serum-based matrix as similar as possible to that of the samples of interest.
Key words
Full text:
1
Collection:
01-internacional
Database:
MEDLINE
Main subject:
Plasma
/
Ascorbic Acid
/
Micronutrients
/
Dietary Supplements
/
Laboratories
Type of study:
Clinical_trials
Aspects:
Implementation_research
Limits:
Humans
Language:
En
Journal:
Anal Bioanal Chem
Year:
2021
Document type:
Article
Affiliation country: