Nelson Bryant C, Pfeiffer Christine M, Zhang Ming, Duewer David L, Sharpless Katherine E, Lippa Katrice A
National Institute of Standards and Technology, Biochemical Science Division, Gaithersburg, MD 20899-0001, USA.
Clin Chim Acta. 2008 Sep;395(1-2):99-105. doi: 10.1016/j.cca.2008.05.016. Epub 2008 May 29.
The National Institute of Standards and Technology (NIST) has recently developed Standard Reference Material (SRM) 1955 Homocysteine and Folate in Frozen Human Serum with certified values for total homocysteine (tHcy) and 5-methyl-tetrahydrofolic acid. NIST has performed an international, interlaboratory assessment of SRM 1955 commutability; results are reported for tHcy only.
Total Hcy was measured in 20 patient sera and in 3 levels of SRM 1955 using 14 immunoassays and/or enzymatic assays. Liquid chromatography/tandem mass spectrometry was utilized as the reference assay. An "errors-in-variables" statistical model was utilized to assess the commutability of SRM 1955.
Normalized residuals ranged from -2.65 to 2.19 for SRM 1955. The median interlaboratory/interassay imprecision (CV) was approximately 4% for patient specimens and ranged from approximately 3% to approximately 7% for SRM 1955. The median intra-assay imprecision ranged from approximately 1% to approximately 13%. Orthogonal residuals, as a descriptor of assay accuracy, ranged from 0.29 to 7.71 and from 0.20 to 2.22 for patient specimens and SRM 1955 samples, respectively.
The current study suggests that SRM 1955 is commutable with the investigated tHcy assays; however, a broader specimen set needs to be evaluated to completely substantiate this conclusion.
美国国家标准与技术研究院（NIST）最近研制出了标准参考物质（SRM）1955——冷冻人血清中的同型半胱氨酸和叶酸，其总同型半胱氨酸（tHcy）和5-甲基四氢叶酸具有认证值。NIST对SRM 1955的互换性进行了一项国际实验室间评估；仅报告了tHcy的结果。
使用14种免疫测定法和/或酶测定法，对20份患者血清和3个水平的SRM 1955中的总同型半胱氨酸进行了测量。液相色谱/串联质谱法用作参考测定法。采用“变量误差”统计模型评估SRM 1955的互换性。
SRM 1955的标准化残差范围为-2.65至2.19。患者标本的实验室间/批间不精密度中位数（CV）约为4%，SRM 1955的不精密度中位数范围约为3%至约7%。批内不精密度中位数范围约为1%至约13%。作为测定准确性描述指标的正交残差，患者标本和SRM 1955样本分别为0.29至7.71和0.20至2.22。
当前研究表明，SRM 1955与所研究的tHcy测定法具有互换性；然而，需要评估更广泛的样本集以完全证实这一结论。
