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CPE-009 · Classification
B12-01: Low serum B12
Low serum B12. Evaluates serum vitamin B12 below 200 pg/mL (148 pmol/L).
Condition
- serum vitamin B12 < 200 pg/mL (148 pmol/L)
What it reports
- Biochemical pattern compatible with vitamin B12 deficiency
Recommended next steps (for physician review)
- Look for the cause: pernicious anemia, diet, drugs (metformin, acid suppression, nitrous oxide), malabsorption
- Confirm with methylmalonic acid when the picture is unclear
Diagnostic boundary
- A pattern for physician review; it does not choose a treatment.
Evidence
- EV-BSH-2014Devalia V, Hamilton MS, Molloy AM; British Committee for Standards in Haematology. Guidelines for the diagnosis and treatment of cobalamin and folate disorders. Br J Haematol. 2014;166(4):496-513.Supports: Diagnostic approach with serum B12, MMA and homocysteine Neurologic involvement means treatment should not wait for confirmation Folic acid alone must not be given while B12 deficiency is unexcluded
- EV-STABLER-2013Stabler SP. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-160.Supports: Clinical presentations, subacute combined degeneration, nitrous oxide and drug causes
Cases where this rule fires
Open a case to see this rule fire with real inputs, then change the values until it stops.
B12-FX-01
B12 of 150 pg/mL with macrocytic anemia
A 67-year-old with MCV 108.
B12-FX-06
Posterior-column signs and spasticity
A pattern compatible with subacute combined degeneration.
B12-FX-08
Low B12 in a 71-year-old with autoimmune thyroid disease and glossitis
Intrinsic-factor antibodies not done.
B12-FX-09
Intrinsic-factor antibodies positive
Pernicious anemia is supported.
B12-FX-10
Hypersegmented neutrophils
MCV 102 and B12 190.
B12-FX-18
Low B12 and low folate
Both are deficient.
B12-FX-20
Pancytopenia with MCV 112
A severe picture.
B12-FX-21
Schistocytes with raised LDH in a macrocytic anemia
Hemolytic features.
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