This is an article from the journal of the American Society Of Haematology. Hope the link works as I went to it from a facebook link from Sally Pacholek: bloodjournal.org/content/12...
Quote: "The mass of accumulated data shows that serum cobalamin is an insensitive assay for B12 deficiency and should be abandoned."
They say that if this test was the only test relied on for diagnosis that patients "would" go untreated. I think this should say patients DO go untreated. They recommend the MMA test instead.