Evaluation of the technical performance of novel holotranscobalamin (holoTC) assays in a multicenter European demonstration project

Abstract

A commercially available holotranscobalamin (holo-TC) radioimmunoassay (RIA) (Axis-Shield, Dundee, Scotland) was evaluated in four laboratories and compared with a holoTC ELISA run in one laboratory. The performance of the holoTC RIA assay was comparable in three of the four participating laboratories. The results from these three laboratories, involving at least 20 initial runs of "low", "medium" and "high" serum-based controls (mean holoTC concentrations 34, 60 and 110 pmol/L, respectively) yielded an intra-laboratory imprecision of 6-10%. No systematic inter-laboratory deviations were observed on runs involving 72 patient samples (holoTC concentration range 10-160 pmol/L). A fourth laboratory demonstrated higher assay imprecision for control samples and systematic deviation of results for the patient samples. Measurement of holoTC by ELISA showed an imprecision of 4-5%, and slightly higher mean values for the controls (mean holoTC concentrations 40, 70 and 114 pmol/L, respectively). Comparable results were obtained for the patient samples. The long-term intra-laboratory imprecision was 12% for the holoTC RIA and 6% for the ELISA. In conclusion, it would be prudent to check the calibration and precision prior to starting to use these holoTC assays in research or clinical practice. The results obtained using the holoTC RIA were similar to those obtained using the holoTC ELISA assay.

Determination of serum holotranscobalamin concentrations with the AxSYM active B12 assay: cut-off point evaluation in the clinical laboratory

“…The 40 pmol/L cut-off value we selected was also reported by other authors (18)(19)(20). We also verified the predictive ability of HoloTC at this threshold for selected tB 12 cut-off points.…”

Metformin and Vitamin B12 Deficiency: Where Do We Stand?

“…The test is thought to have sensitivities and specificities comparable to that of serum vitamin B12 when compared to MMA elevations (48). Several studies suggested that holo-TC-II slightly outperformed the serum vitamin B12 test (65,66). The specificity of the holo-TC-II test remains unclear.…”

“…Laboratories use cut-offs that range between 11 and 41 pmol/L (66). Relationships between chosen cut-offs and resultant outcomes warrant additional research.…”

“…Mild renal insufficiency has a modest impact on serum vitamin B12 and holo-TC-II levels, unlike its effect on MMA and homocyteine concentrations (59). Several studies suggested that the levels of holo-TC-II are affected by folate disorders, use of oral contraceptives, myelodysplasia, certain hematologic disorders and alcoholism (66,68,69). Having the half-life of just six minutes and being dependent on the absorbed vitamin B12, holo-TC-II levels may fluctuate following dietary perturbations (70).…”

Vitamin B12 absorption judged by measurement of holotranscobalamin, active vitamin B12: evaluation of a commercially available EIA kit

“…We used the Axis-Shield active B12 EIA kit (9) and diluted samples 1:1 in sample diluents according to the kit insert. In addition, we used our in-house ELISA (7,10) . The two samples obtained as part of the CobaSorb test are always run on the same day and, because of that, our main interest was to explore the intra-assay variation of the EIA kit.…”