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CPE-009 · synthetic case B12-FX-04
Macrocytic anemia, folic acid ordered, no B12
A safety situation.
Purpose: A safety situation.
Inputs the engine received
Laboratory
- MCV
- 112 fL
- Hemoglobin
- 9.1 g/dL
Patient
- Age
- 57 years
- Sex
- Female
- Folic acid ordered or planned
- Yes
What the engine reports
Correcting a megaloblastic anemia with folic acid alone can mask vitamin B12 deficiency while neurologic damage progresses. Measure vitamin B12 before, or together with, any folic acid.
Detected clinical pattern
Measure B12 Before Folic Acid
A macrocytic anemia with folic acid planned and no B12 on file is a safety situation.
Recommended next steps
For physician consideration. Urgent review always comes first.
- 1Measure vitamin B12 before or together with any folic acid treatment.
- 2Check B12 and folate, a reticulocyte count and a blood film; review alcohol, liver and thyroid status and drugs.
Differentials, pitfalls and contradicting signals
- Macrocytosis has many causes beyond B12 and folate: alcohol, liver disease, hypothyroidism, reticulocytosis, myelodysplasia and drugs (hydroxyurea, methotrexate, zidovudine, azathioprine).
Missing information
- Vitamin B12 level.
Evidence and rule trace · 3 rules
B12-04Folic acid before B12 status is known
Inputs: MCV 112 fL · folic acid ordered or planned · B12 not measured
Safety: folic acid alone can mask B12 deficiency.
Evidence
- EV-BSH-2014 · Devalia 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.
- EV-STABLER-2013 · Stabler SP. Vitamin B12 deficiency. N Engl J Med. 2013;368(2):149-160.
Physician adjudication required. Clinical decision support for physician review. This output identifies laboratory patterns and safety considerations. It does not diagnose, find the cause, or select a vitamin product, dose or route. Physician adjudication is required.
Change the values
The same engine, starting from this case. Change any value and watch the pattern and the rule trace react.
Serum B12 level
○ Below 200 pg/mL
Deficiency pattern
○ 200 to 300 pg/mL
Borderline: MMA and homocysteine settle it
○ Above 300 pg/mL
Deficiency unlikely, not excluded
No stage is assigned for the values entered.
Laboratory
- <200
- 200–300
- >300
Patient
Neurologic features
Drugs, diet and risk groups
More b12 cases
B12-FX-01
B12 of 150 pg/mL with macrocytic anemia
A 67-year-old with MCV 108.
B12-FX-02
Borderline B12 with raised MMA
B12 260 and MMA 0.52.
B12-FX-03
Borderline B12 and no confirmatory test
B12 250.
B12-FX-05
Neuropathy, B12 220 and metformin for five years
Neurologic features with a borderline level.
B12-FX-06
Posterior-column signs and spasticity
A pattern compatible with subacute combined degeneration.
B12-FX-07
Macrocytosis in a patient with alcohol use disorder
MCV 104, B12 not measured.
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