The most direct and specific test to diagnose vitamin B12 deficiency is the measurement of serum vitamin B12 level. A low level confirms the deficiency. However, it's important to note that some patients with neurological symptoms due to B12 deficiency may have borderline-low levels. In such cases, or if the clinical suspicion is high despite a normal B12 level, measuring metabolites like methylmalonic acid (MMA) and homocysteine can be helpful. These substances accumulate when B12 is deficient because B12 is a cofactor in the enzymes that metabolize them. Elevated MMA is more specific for B12 deficiency, while homocysteine can be elevated in both B12 and folate deficiency. A bone marrow exam would show megaloblastic changes but is invasive and not a first-line test. Serum folate measures folate, not B12.

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Zambia

• Joseph Soko – 101 pts

• Visual Pathway Lesions
• Positive and Negative Symptoms
• Hallucinations and Delusions
• Antipsychotic Medications
• Emergency: Environmental Emergencies