Unexplained Elevated Vitamin B12: Consider Macro-B12.

Area of Science:

• Clinical Chemistry
• Hematology
• Immunology

Background:

• Elevated vitamin B12 can stem from various causes, including supplementation, liver/kidney disease, or myeloid malignancies.
• Persistent high vitamin B12 may cause patient anxiety and lead to invasive diagnostics.
• Macro-B12, a complex of vitamin B12, transcobalamin, and immunoglobulins, is a benign cause of elevated vitamin B12 due to reduced clearance.

Purpose of the Study:

• To investigate the utility of polyethylene glycol (PEG) precipitation in identifying macro-B12.
• To assess if macro-B12 can prevent unnecessary invasive diagnostic procedures.
• To study the prevalence of macro-B12 in patients with and without myeloid malignancies.

Main Methods:

• Polyethylene glycol (PEG) precipitation assay was employed to detect macro-B12.
• A case study illustrated PEG precipitation's potential to avert a bone marrow biopsy.
• Macro-B12 presence was evaluated in patients with elevated vitamin B12, with and without myeloid malignancies.

Main Results:

• Macro-B12 was identified in 24% of 72 individuals with vitamin B12 > 1476 pmol/L.
• One patient with macro-B12 showed functional vitamin B12 deficiency (elevated methylmalonic acid).
• Macro-B12 was not detected in 8 patients with myeloid malignancy.

Conclusions:

• PEG precipitation can help identify macro-B12 as a cause of elevated vitamin B12.
• This assay may prevent unnecessary diagnostic procedures, such as bone marrow punctures, in select patients.
• Macro-B12 is not associated with myeloid malignancies in this study cohort.