Griffioen Pieter H, van Dam-Nolen Dianne H K, Lindemans Jan, Heil Sandra G
Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands.
Erasmus MC University Medical Center Rotterdam, Department of Clinical Chemistry, PO box 2040, 3000 CA Rotterdam, The Netherlands.
Clin Biochem. 2017 Dec;50(18):1030-1033. doi: 10.1016/j.clinbiochem.2017.08.009. Epub 2017 Aug 16.
Vitamin B12 deficiency is mostly caused by insufficient gastro-intestinal absorption and in rare conditions by Transcobalamin (TC) deficiency. Unsaturated Transcobalamin (apoTC) can be measured by a binding assay using radiolabeled cobalamin. The Active B12 test analyzes saturated Transcobalamin (holoTC) and we hypothesize that this test can be used to measure total TC by additional in vitro saturation with cobalamin.
Serum was saturated in vitro (16 times dilution) with a cyanocobalamin solution and total TC was selectively measured with the Abbott Active B12 test. ApoTC was calculated by subtracting endogenous holoTC from total TC after correction for dilution. Linearity was determined with a pool serum dilution series. Precision was investigated according to the CLSI EP15 protocol. Method comparison was performed against a binding assay using radiolabeled cobalamin. Reference values were determined in 100 healthy controls.
The method was linear in the range of 240 to 1933pmol/L (R=0.997, lack of fit F=1.61). Precision of low- and high-pool total TC in serum were; 5.2% and 4.3% respectively. Method comparison against a radiolabeled cobalamin binding assay showed a proportional bias of 30% (y=0.70x+126). Total TC reference values were determined at 500-1276pmol/L.
We describe a rapid method to quantify total TC, which can be implemented on routine platforms using commercial Active B12 tests. In addition, apoTC can be assessed by subtracting endogenous holoTC concentration which can be measured in the same run, securing the same calibration level for all three parameters (holoTC, apoTC and total TC). This method is applicable in clinical diagnostics and in larger epidemiological studies.
维生素B12缺乏主要由胃肠道吸收不足引起，在极少数情况下由转钴胺素（TC）缺乏引起。不饱和转钴胺素（apoTC）可通过使用放射性标记钴胺素的结合试验来测量。活性B12试验分析饱和转钴胺素（holoTC），我们假设该试验可通过用钴胺素进行额外的体外饱和来测量总TC。
血清在体外（16倍稀释）用氰钴胺溶液饱和，并用雅培活性B12试验选择性测量总TC。apoTC通过在校正稀释后从总TC中减去内源性holoTC来计算。用混合血清稀释系列确定线性。根据CLSI EP15协议研究精密度。与使用放射性标记钴胺素的结合试验进行方法比较。在100名健康对照中确定参考值。
该方法在240至1933pmol/L范围内呈线性（R = 0.997，失拟F = 1.61）。血清中低池和高池总TC的精密度分别为5.2%和4.3%。与放射性标记钴胺素结合试验的方法比较显示比例偏差为30%（y = 0.70x + 126）。总TC参考值确定为500 - 1276pmol/L。
我们描述了一种快速定量总TC的方法，该方法可使用商业活性B12试验在常规平台上实施。此外，apoTC可通过减去可在同一次运行中测量的内源性holoTC浓度来评估，确保所有三个参数（holoTC、apoTC和总TC）具有相同的校准水平。该方法适用于临床诊断和更大规模的流行病学研究。
