Welch M J, Hertz H S
Center for Analytical Chemistry, National Bureau of Standards, Gaithersburg, MD 20899.
Arch Pathol Lab Med. 1988 Apr;112(4):343-5.
The National Bureau of Standards (NBS) has been involved for more than ten years in development of definitive methods for measuring important inorganic and organic analytes in human serum, including calcium, potassium, chloride, cholesterol, glucose, urea, uric acid, and creatinine. These methods are carefully designed and thoroughly tested isotope dilution mass spectrometric procedures that produce results of high precision and accuracy. Definitive methods are used to certify concentrations in reference serum pools, which are distributed among clinical laboratories as a means of assessing the accuracy of the routine methods. The College of American Pathologists operates a major proficiency testing program for clinical laboratories. The National Bureau of Standards works with the College of American Pathologists to assign values for analyte concentrations in proficiency testing samples where possible, and these values are used to assess the overall accuracy of the participants (grand mean) as well as the accuracy of peer groups (those that use the same methodology and/or instrumentation). For the analytes studied to date, the grand mean values have generally been close to the definitive values, but some of the peer group results have shown significant biases. To illustrate the definitive method development process, a modified and improved definitive method for cholesterol measurement is described. The modified method uses a cholesterol-13C3 as the labeled internal standard, capillary gas chromatography for sample introduction, and a novel means of electrically switching between the ions being measured. Results on standard reference material 909, a lyophilized human serum, demonstrate the precision and absence of significant measurement bias attainable with the new method.
美国国家标准局（NBS）十多年来一直致力于开发用于测量人血清中重要无机和有机分析物的权威方法，这些分析物包括钙、钾、氯、胆固醇、葡萄糖、尿素、尿酸和肌酐。这些方法是经过精心设计和全面测试的同位素稀释质谱程序，可产生高精度和高准确度的结果。权威方法用于认证参考血清库中的浓度，这些血清库分发给临床实验室，作为评估常规方法准确性的一种手段。美国病理学家学会为临床实验室开展一项主要的能力验证计划。美国国家标准局与美国病理学家学会合作，尽可能为能力验证样本中的分析物浓度赋值，这些值用于评估参与者的总体准确性（总体均值）以及同组参与者（使用相同方法和/或仪器的参与者）的准确性。对于迄今为止所研究的分析物，总体均值通常接近权威值，但一些同组参与者的结果显示出显著偏差。为说明权威方法的开发过程，本文描述了一种经过改进的胆固醇测量权威方法。改进后的方法使用胆固醇 -13C3 作为标记内标，采用毛细管气相色谱进样，并采用一种新颖的方法在被测量离子之间进行电切换。对冻干人血清标准参考物质 909 的检测结果证明了该新方法可达到的精密度以及不存在显著测量偏差。
