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[Homocysteine and methylmalonic acid. New tests--for what benefit?]
1Hematologisk seksjon, Haukeland Sykehus, Bergen.
Summary
Diagnosing vitamin B12 deficiency requires low serum cobalamin (<250 pmol/l) with elevated homocysteine and methylmalonic acid. Folate deficiency is confirmed by low folate and high homocysteine. If cobalamin is >250 pmol/l, no further testing is needed.
Area of Science:
- Biochemistry
- Clinical Diagnostics
- Nutritional Science
Context:
- Accurate diagnosis of vitamin B12 deficiency is crucial for preventing neurological complications.
- Elevated homocysteine and methylmalonic acid are key indicators, but their interpretation requires context.
Purpose:
- To outline diagnostic criteria for vitamin B12 and folate deficiencies.
- To clarify the role of homocysteine and methylmalonic acid in diagnosing these deficiencies.
Summary:
- Vitamin B12 deficiency is confirmed by serum cobalamin <250 pmol/l, high plasma homocysteine, and high serum methylmalonic acid.
- Folate deficiency is indicated by low serum/erythrocyte folate and high plasma homocysteine.
- Elevated homocysteine and methylmalonic acid that decrease with vitamin B12 therapy suggest deficiency in patients with neurological/psychiatric symptoms.
Impact:
- Provides clear diagnostic guidelines for clinicians.
- Highlights the limitations of homocysteine as a standalone screening test.
- Aids in the timely and accurate identification of vitamin deficiencies.