Prevention Based on Laboratory Tests to Dismantle Paradoxical B12 Hypervitaminemia: A Case Report with a Critical Review of the Literature

Elevated levels of vitamin B12 (B12 hypervitaminemia) greater than 1000 pg/mL can be toxic and may serve as a marker for conditions such as cancer, autoimmune inflammatory diseases, or renal or hepatic failure. B12 hypervitaminemia, a complex generated by the binding of monomeric vitamin B12 and existing immunoglobulins in serum, can be detected in most available immunoassays. The purpose of this work was twofold: firstly, to evaluate a technique such as polyethylene glycol (PEG) precipitation in samples, before vitamin B12 determination, to prove that not all cases of B12 hypervitaminemia are related to oncological pathologies or serious diseases, and secondly, to address the patient’s condition. Materials and methods: Serum samples were collected from the patient and pre-treated with PEG. Baseline vitamin B12 levels and vitamin B12 levels in the supernatant following PEG precipitation were detected by chemiluminescence. Results: Ten samples were analysed in two different laboratories, classified as public and private; in all cases, vitamin B12 levels were above 1000 pg/mL, with a mean of 2550 pg/mL (1738–3899 pg/mL). PEG precipitation resulted in an 84.25% reduction in vitamin B12 levels. Conclusions: In cases of B12 hypervitaminemia in which there is no correlation between patient clinical symptoms and detected vitamin B12 levels, the PEG immunoprecipitation test before vitamin B12 determination is a simple and low-cost laboratory technique that can be routinely used in clinical practice to determine actual vitamin B12 levels. The technique would spare patients unnecessary complementary tests and inappropriate treatments.