Section of Hematology and Coagulation, Sahlgrenska Academy, University of Gothenburg, Sweden.
Ann Clin Biochem. 2013 Nov;50(Pt 6):585-94. doi: 10.1177/0004563212474939. Epub 2013 Jul 30.
Subclinical cobalamin deficiency is common in the elderly, but the sensitivity and specificity of serum total cobalamin for this diagnosis is poor. Serum holotranscobalamin (holoTC), a measure of biologically available cobalamin, is considered a better marker for early cobalamin depletion than total cobalamin. However, in elderly populations, health-related reference intervals for holoTC and correlations to renal function are not entirely clear.
HoloTC was determined with an automated microparticle enzyme immunoassay (AxSYM®) in 790 elderly non-vitamin-supplemented Swedish men, median age 75.3 years. Renal function was assessed with creatinine, cystatin C and estimated glomerular filtration rate (eGFR calculated from creatinine).
Median holoTC was 51.8 pmol/L, the health-related reference interval 19.6-132.3 pmol/L. There was no significant difference in mean holoTC in probands with normal compared to high creatinine (P = 0.80) and cystatin C (P = 0.82). No significant differences between the quartiles of creatinine or cystatin C in mean of log holoTC were seen. HoloTC correlated strongly with total cobalamin (r = 0.69, P < 0.001), weaker with eGFRcreatinine (r = -0.09, P < 0.05) and creatinine (r = 0.09, P < 0.05), the latter correlation was only seen in subjects with creatinine <100 µmol/L. HoloTC correlated negatively with plasma total homocysteine (r = -0.24, P < 0.001), but not with cystatin C and age.
Serum holoTC in healthy elderly men shows the same distribution as earlier described for a younger reference population. In this group of elderly subjects, holoTC did not correlate to reduced renal function. Thus, holoTC appears to be a promising tool for evaluating cobalamin status also in elderly populations.
亚临床钴胺素缺乏在老年人中很常见，但血清总钴胺素对此诊断的敏感性和特异性较差。血清全钴胺素（holoTC），一种衡量生物可利用钴胺素的指标，被认为是比总钴胺素更早检测出钴胺素耗竭的更好标志物。然而，在老年人群中，holoTC 的健康相关参考区间及其与肾功能的相关性尚不完全清楚。
在 790 名未服用维生素的瑞典老年男性中，采用自动化微粒子酶免疫分析法（AxSYM®）测定 holoTC，中位年龄 75.3 岁。采用肌酐、胱抑素 C 和估算肾小球滤过率（eGFR 由肌酐计算得出）评估肾功能。
中位 holoTC 为 51.8 pmol/L，健康相关参考区间为 19.6-132.3 pmol/L。与肌酐较高（P=0.80）和胱抑素 C 较高（P=0.82）的患者相比，正常肌酐的患者的平均 holoTC 没有显著差异。肌酐或胱抑素 C 的四分位数之间，log holoTC 的平均值没有显著差异。holoTC 与总钴胺素呈强相关（r=0.69，P<0.001），与 eGFRcreatinine（r=-0.09，P<0.05）和肌酐（r=0.09，P<0.05）呈弱相关，后一种相关性仅见于肌酐<100 μmol/L 的患者。holoTC 与血浆总同型半胱氨酸呈负相关（r=-0.24，P<0.001），但与胱抑素 C 和年龄无关。
健康老年男性的血清 holoTC 分布与以前描述的年轻参考人群相同。在这群老年受试者中，holoTC 与肾功能降低无关。因此，holoTC 似乎是评估老年人群钴胺素状态的一种很有前途的工具。
