v46 一位病患疑似有維生素B12缺乏現象，下列何種血液變化最不支持此一診斷？

甲基丙二酸（methylmalonic acid）過高

對羥基苯丙酮酸（para-hydroxyphenylpyruvate）過高

紅血球過少

巨母紅血球過多

b

Pathology

Increased methylmalonic acid levels may indicate a vitamin B₁₂ deficiency. However, it is sensitive without being specific. MMA is elevated in 90-98% of patients with B₁₂ deficiency. This test may be overly sensitive, as 20-25% of patients over the age of 70 have elevated levels of MMA, but 25-33% of them do not have B₁₂deficiency. For this reason, MMA is not routinely recommended in the elderly.