Rasmussen K
Klinisk biokemisk afdeling, Skejby Sygehus, Arhus.
Ugeskr Laeger. 1996 Jul 1;158(27):3913-8.
The clinical value of measuring concentrations of methylmalonate and total homocysteine in plasma as an aid in the diagnosis of cobalamin, folate and pyridoxine deficiencies has recently aroused interest. This review describes factors which affect the validity and interpretation of plasma (p-) methylmalonate and p-homocysteine. P-methylmalonate is not affected by preanalytical variables, there are no age- or sex-related differences and the intra-individual variation is negligible. The only important limitation to the specificity of an increased p-methylmalonate for cobalamin deficiency appears to be secondary accumulation due to impaired renal function. However, an elevated p-methylmalonate, which normalizes following cobalamin injections proves cobalamin deficiency, irrespective of renal function. P-homocysteine is affected by several preanalytical factors, so the utmost care is required in blood collection. Furthermore, p-homocysteine is dependent on age and sex. An elevated p-homocysteine is a less specific parameter for cobalamin deficiency, for which reason measurement in patients with suspected cobalamin deficiency is indicated only if p-methylmalonate is normal. Homocysteine is also increased in folate and pyridoxine deficiencies. Recently, moderate hyperhomocysteinaemia has become an established independent and significant risk factor for premature atherosclerotic cardiovascular diseases, suggesting a large future demand for p-homocysteine determinations.
测量血浆中甲基丙二酸和总同型半胱氨酸浓度以辅助诊断钴胺素、叶酸和吡哆醇缺乏症的临床价值最近引起了人们的关注。这篇综述描述了影响血浆（p-）甲基丙二酸和p-同型半胱氨酸有效性及解读的因素。p-甲基丙二酸不受分析前变量影响，不存在年龄或性别相关差异，个体内差异可忽略不计。p-甲基丙二酸升高对钴胺素缺乏特异性的唯一重要限制似乎是由于肾功能受损导致的继发性蓄积。然而，注射钴胺素后恢复正常的升高的p-甲基丙二酸可证明钴胺素缺乏，与肾功能无关。p-同型半胱氨酸受多种分析前因素影响，因此采血时需要格外小心。此外，p-同型半胱氨酸取决于年龄和性别。p-同型半胱氨酸升高对钴胺素缺乏来说是一个特异性较低的参数，因此仅在p-甲基丙二酸正常时才建议对疑似钴胺素缺乏的患者进行测量。同型半胱氨酸在叶酸和吡哆醇缺乏时也会升高。最近，中度高同型半胱氨酸血症已成为早发性动脉粥样硬化性心血管疾病既定的独立且重要的危险因素，这表明未来对p-同型半胱氨酸检测的需求很大。
