2015-10-24-世界卫生组织-WHO_BS_2015.2263_Report_of_the_international_collaborative_study_to_assign_a_holotranscobalamin_holoTC_value_to_the_IS_for_folate_and_B12_03_178_27页_728kb

Summary of the International Collaborative Study on Holotranscobalamin (holoTC)

Purpose

To assign a holotranscobalamin (holoTC) value to the existing 1st International Standard for serum folate and vitamin B12 (03/178). The goal was to facilitate standardization of holoTC assays.

Background

• B12 Role: Vitamin B12 (cobalamin) is essential for DNA synthesis. The active form, holoTC, is superior for early B12 deficiency detection compared to total B12.
• WHO Standard: The standard (03/178), established in 2005, has values of 12.1 nmol/L for folate and 480 pg/mL for B12.

Study Design

• Participants: 12 laboratories from 8 countries.
• Runners: Included manufacturers, clinical, and research labs.
• Methods: Used commercial and in-house immunoassays for holoTC measurement.
• Materials: WHO Standard (03/178) and three serum samples with varying holoTC levels.
• Procedure: Each lab prepared two independent doubling dilution series over three days, measuring holoTC contents.

Results and Statistical Analysis

• Assigned HoloTC Value: 107 pmol/L for the standard.
• Inter-laboratory Variability: Geometric Coefficient of Variation (GCV) 10.5%.
• Statistics: Unweighted geometric means were used; 14 outlier results were excluded.
• Serial Plasma Stability: The standard remained stable at -20°C, with only a 0.035% potency loss per year.

Findings

• The international standard displayed good commutability, reducing inter-laboratory variability when compared to assay calibrations.

Proposal

WHO is seeking approval to assign a holotranscobalamin value of 107 pmol/L to the existing standard, IS (03/178).

Implementation Plan

-inform manufacturer and user communities,

• Promote via UK NEQAS scheme,
• Update product catalog and newsletter,
  -publish in an international scientific journal.