Allen R H, Stabler S P, Savage D G, Lindenbaum J
Department of Medicine, University of Colorado Health Sciences Center, Denver 80262.
Am J Hematol. 1990 Jun;34(2):90-8. doi: 10.1002/ajh.2830340204.
The serum cobalamin assay is the primary diagnostic test for cobalamin deficiency. It appears to be an excellent screening test since most patients with clinically confirmed cobalamin deficiency have low levels. Recent studies indicate that the clinical picture of cobalamin deficiency is much more diverse than previously believed. It is also apparent that many patients with low serum cobalamin concentrations are not cobalamin deficient. Thus, there is a need for additional diagnostic tests to further distinguish patients with low serum cobalamin levels who are actually cobalamin deficient and will benefit from lifetime treatment from those who are not deficient and will not benefit. Serum levels of methylmalonic acid and total homocysteine have been shown to be markedly elevated in most patients with cobalamin deficiency, and total homocysteine concentrations are markedly elevated in most patients with folate deficiency. The levels of these metabolites fall to normal if these patients are treated with the appropriate vitamin but remain essentially unchanged if the wrong vitamin is administered. These observations demonstrate that serum methylmalonic acid and total homocysteine levels are useful in diagnosing patients with cobalamin and folate deficiency and in distinguishing between these two vitamin deficiencies.
血清钴胺素测定是钴胺素缺乏的主要诊断测试。由于大多数临床确诊为钴胺素缺乏的患者水平较低，它似乎是一项出色的筛查测试。最近的研究表明，钴胺素缺乏的临床表现比以前认为的要多样化得多。同样明显的是，许多血清钴胺素浓度低的患者并非钴胺素缺乏。因此，需要额外的诊断测试来进一步区分血清钴胺素水平低但实际缺乏钴胺素且将从终身治疗中受益的患者与不缺乏钴胺素且不会受益的患者。大多数钴胺素缺乏患者的血清甲基丙二酸和总同型半胱氨酸水平已显示明显升高，大多数叶酸缺乏患者的总同型半胱氨酸浓度也明显升高。如果这些患者用适当的维生素治疗，这些代谢物的水平会降至正常，但如果给予错误的维生素，其水平基本保持不变。这些观察结果表明，血清甲基丙二酸和总同型半胱氨酸水平有助于诊断钴胺素和叶酸缺乏患者，并区分这两种维生素缺乏症。
