Test Database

Description

The Architect Active- B12 assay is a two-step immunoassay for the quantitative determination of holotranscobalamin in human serum using chemiluminescent microparticle immunoassay (CMIA) technology Due to the relocation of the Nutristasis service to the Blackfriars Hub site, this test is not currently accredited by UKAS to ISO15189.

Clinical details

The current convention is to estimate the abundance of vitamin B12 using total serum vitamin B12 as the first-line screen for deficiency. However this test has a low sensitivity. Up to 45% of vitamin B12-deficient/insufficient subjects may be overlooked if only serum B12 is used as a screening test. Active B12 (holotranscobalamin - holoTC) is the metabolically active portion of B12. Emerging evidence indicates that a low level of Active B12 is a more reliable marker of impaired vitamin B12 status than a low level of serum vitamin B12. Moreover unlike serum B12, Active B12 is believed to be stable in pregnancy. Several studies support Active B12 measurement as a first-line diagnostic test, and suggest that Active B12 may be the earliest marker for B12 depletion.

Related condition

Vitamin B12 deficiency, transcobalamin deficiency/Pernicious anaemia, ileal disease, chronic malnutrition, atrophic gastritis, achlorhydria, infection with Helicobacter pylori.

Reference range

>70*; * between 25-70 referred for MMA

Units

pmol/L

Synonyms

holoTC, holotranscobalamin, holoTC II, TC-B12/vitamin B12 deficiency, pernicious anaemia

Testing site

Synnovis : Reference Services : Blackfriars Hub

Laboratory

Nutristasis Unit