UK NEQAS Haematinics Scheme for Haematinics, Good Hope Hospital, Sutton Coldfield, UK.
Clin Chem. 2011 Jul;57(7):986-94. doi: 10.1373/clinchem.2010.160135. Epub 2011 May 5.
Current methods for measuring folates in clinical laboratories are competitive folate binding protein assays. These assays show a considerable lack of agreement that has implications for the comparability of data across studies as well as for long-term population studies. The development of isotope dilution-liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) reference methods permitted the evaluation of method accuracy and consistency over time.
We measured 3 pools of human serum by ID-LC-MS/MS, calculated values for total folate, and distributed the same pools to participants in a national External Quality Assessment scheme. We used linear regression to compare the all-laboratory and method data with reference method values. The exercise was repeated after 18 months to assess the stability of the all-laboratory and method data.
The distributed serum pools had mass spectrometry values for folate species typical of those found in healthy individuals from populations not receiving dietary folic acid fortification. There was good agreement of the all-laboratory data set with the reference method (y =0.86x + 0.91 μg/L) at both time points. Linear regression demonstrated that the Abbott Architect showed the closest agreement with the reference method. The Roche Elecsys method was nonlinear and showed a calibration offset of 2.6 μg/L (4.57 nmol/L).
Calibration of serum folate assays traceable to higher-order reference methods increases method accuracy and improves consistency. The all-laboratory consensus mean proved sufficiently accurate and stable to be used as the target for monitoring laboratory performance.
目前临床实验室中用于检测叶酸的方法是竞争叶酸结合蛋白检测法。这些检测方法之间存在明显的不一致性，这不仅影响到不同研究之间数据的可比性，也影响到长期的人群研究。同位素稀释-液相色谱-串联质谱法（ID-LC-MS/MS）参考方法的开发使得我们能够评估方法的准确性和随时间推移的一致性。
我们使用 ID-LC-MS/MS 方法测量了 3 个人血清池，计算了总叶酸值，并将相同的血清池分发给全国外部质量评估计划的参与者。我们使用线性回归比较了所有实验室和方法数据与参考方法值。18 个月后，我们重复了该实验，以评估所有实验室和方法数据的稳定性。
分发的血清池的质谱值具有未接受叶酸强化的人群中健康个体的典型叶酸物种特征。在两个时间点，所有实验室数据组与参考方法（y=0.86x+0.91μg/L）均具有良好的一致性。线性回归表明，雅培 Architect 与参考方法的一致性最好。罗氏 Elecsys 方法是非线性的，校准偏移为 2.6μg/L（4.57nmol/L）。
可溯源至更高阶参考方法的血清叶酸检测的校准可提高方法的准确性并提高一致性。所有实验室的共识平均值证明足够准确和稳定，可用于监测实验室性能。
