NIST/NCI Micronutrients Measurement Quality Assurance Program: Measurement Repeatabilities and Reproducibilities for Fat-Soluble Vitamin-Related Compounds in Human Sera

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• 作者：David L. Duewer ; Jeanice Brown Thomas ; Margaret C. Kline ; William A. MacCrehan ; Robert Schaffer ; Katherine E. Sharpless ; Willie E. May ; and James A. Crowell
• 刊名：Analytical Chemistry
• 出版年：1997
• 出版时间：April 1, 1997
• 年：1997
• 卷：69
• 期：7
• 页码：1406 - 1413
• 全文大小：192K
• 年卷期：v.69,no.7(April 1, 1997)
• ISSN：1520-6882

文摘

The NIST/NCI Micronutrient Measurement Quality Assurance Program has conducted 33 interlaboratory comparison exercises for fat-soluble vitamin-related compounds in human sera over the past 12 years. Periodicreanalysis of lyophilized serum samples prepared frommore than 70 different sera has enabled estimation of theshort- and long-term measurement characteristics. Median- and interquartile-range-based statistics adequatelyestimate the distribution of results from laboratoriesthatare in analytical control from total distributions thatinclude a significant minority of outlier data.Short-terminterlaboratory reproducibility standard deviations (SDs)are predictable functions of analyte concentration, withan asymptotic limit at low analyte concentration and alinear relationship at high concentrations. Long-termtrends in the interlaboratory reproducibility can be estimated by standardizing the short-term SD at the observedanalyte concentration to an expected SD at a givenphysiologically significant analyte concentration.The"average" laboratory's same-day analyticalrepeatabilitySD is about one-third of the estimated interlaboratoryreproducibility; repeatability for longer periods betweenanalyses is, on average, no better than thereproducibility.While a few exceptional laboratories have maintainedexcellent repeatability over the entire decade, long-termstudy measurements generated within a single laboratoryare not generally more internally consistent than resultsfrom multiple laboratories. Enhanced and more consistently implemented intralaboratory quality control andquality assurance methods are required to further improve and maintain interlaboratory measurement comparability.