Evaluation of a candidate reference measurement procedure for serum free testosterone based on ultrafiltration and isotope dilution-gas chromatography-mass spectrometry

BACKGROUND: To assess the analytical validity of free testosterone (FTe) measurements, a reference measurement procedure (RMP) is required. For steroids, isotope dilution-mass spectrometry is accepted as state-of-the-art technology. Because FTe is defined as the hormone fraction in serum water in equilibrium with the protein-bound fraction, the RMP should include a physical separation step. The use of equilibrium dialysis (ED) or ultrafiltration (UF) is advocated. Our objective was to develop such a candidate RMP. METHODS: We selected UF combined with isotope dilution-gas chromatography-mass spectrometry (ID-GC/MS) for direct measurement of Te in the ultrafiltrate. After optimization of the UF process, the complete procedure was validated by use of split-sample comparisons with indirect ED (iED) and symmetric dialysis (SyD). RESULTS: The candidate RMP gave maximum within-day, between-day, and total CVs of 3.0%, 3.1%, and 4.3%. The Deming regression equations for the respective method comparisons were: UF-ID-GC/MS = 0.98(iED) - 53 pmol/L (r = 0.94; S(y|x)= 42 pmol/L) and UF-ID-GC/MS = 0.92(SyD) + 21 pmol/L (r = 0.97; S(y|x)= 31 pmol/L). CONCLUSIONS: We achieved the objective of a state-of-the-art candidate RMP, which agreed well with iED and SyD. However, we also demonstrated that a degree of discordance remains, which may require a decision from an authoritative organization on the recommended procedure to measure free hormone concentrations.     

Estradiol-17 beta quantified in serum by isotope dilution-gas chromatography-mass spectrometry: reversed-phase C18 high-performance liquid chromatography compared with immuno-affinity chromatography for sample pretreatment

Here, isotope dilution-gas chromatography-mass spectometry is used as a reference technique for determining the concentration of estradiol-17 beta in candidate human serum Reference Material. The accuracy of assigned concentrations in biologic materials is not only determined by instrumental performance, it also depends greatly on the selectivity of the procedure for isolating the analyte from the biological matrix, an issue which we consider insufficiently addressed in the literature. We introduced reversed-phase C18 high-performance liquid chromatography as a fractionation procedure in addition to the commonly used solvent extraction and column chromatography on Sephadex LH-20. The validity of this approach as part of a Reference Method for measurement of estradiol-17 beta by isotope dilution-gas chromatography-mass spectrometry was investigated by comparison with immuno-affinity chromatography, which on theoretical grounds is generally considered as highly selective.     

Validation of 5 routine assays for serum free testosterone with a candidate reference measurement procedure based on ultrafiltration and isotope dilution-gas chromatography-mass spectrometry

BACKGROUND/METHOD: The analytical validity of free testosterone (FTe) analog immunoassays is subject to much controversy. We revisited the validation of 4 analog assays and 1 FTe calculation procedure with a metrologically traceable reference measurement procedure (RMP) based on ultrafiltration and isotope dilution-mass spectrometry for direct measurement of Te in the ultrafiltrate. To this end, we performed split-sample measurements of 40 male sera. RESULTS: Deming regression showed that 3 of the immunoassays had moderate to good correlation (0.8474 < or = r < or = 0.9241) with the RMP; however, the slope was markedly below 1. The FTe calculation procedure was in good agreement with this result. The Sy/x values for all assays were higher than the combined imprecision values, which indicate their susceptibility to matrix-related effects. CONCLUSIONS: The study demonstrated substantial differences in analytical quality of FTe assays; however, the results suggested that after extending the validation with a larger variety of samples, recalibration of some analog assays might be worth further investigation.     

离子色谱法测定血清锂离子候选参考方法的建立及性能评估

目的：以离子色谱法为基础,建立血清总锂离子测定的候选参考方法并评价其性能。方法采用一种简单的样本前处理方法,用新鲜患者血清样本、IFCC-RELA 样本等对方法的精密度进行评估;用加标回收实验评价方法的准确性。结果锂离子标准曲线线性方程为：Y ＝0．8171X -0．0013,r^2＝0．99995,方法的检出限为6μg/L;测量血清样本的不精密度（CV）小于1．0％;样本的加标回收率在99％～101％之间。结论成功建立了血清锂候选参考方法,可用于血清锂离子项目的量值溯源和标准化,为血清锂常规检测系统向参考方法/参考物质溯源提供了有效途径。     

A candidate reference method for the determination of magnesium in serum

A candidate reference method for the determination of magnesium in serum (analytical range 0.5 to 2.0 mmol/l) by flame atomic absorption spectrometry was commissioned. The relative standard deviation of the 4 replicates of each value ranged from 0.18 to 1.07%, and the standard error of the mean ranged from 0.63 to 8.34 mumol/l. In the analysis of 3 different standard solutions (prepared by weighing the analyte), which was performed in each of three different experiments the values recorded by the candidate reference method deviated by -0.15, 0.44 and 0.24%, respectively. The reference method value did not differ significantly from the definitive value. As the method seems to be as reliable as comparable reference methods for the determination of sodium, potassium or calcium, tests of transferability should now be undertaken.     

同位素稀释液相色谱串联质谱法测定血清肌酐

目的 建立一种使用同位素稀释液相色谱串联质谱法(ID-LC/MS/MS)测定血清肌酐的候选参考方法.方法 以[2H3]肌酐为内标,用无水乙醇沉淀血清中的蛋白质,用氯仿纯化上清液,用液相色谱串联质谱分离测定,以包括法定量.结果 血清肌酐测定的批内、批间和总变异系数的平均值分别为0.57%(范围0.52%～0.61%)、0.43%(范围0.11%～0.59%)和0.73%(范围0.62%～0.83%).加样回收试验的回收率范围为99.09%～101.13%.分析两种参考物质SRM909b和SRM 967b,测定结果与认定值的偏差小于0.4%.结论 建立了ID-LC/MS/MS法测定血清肌酐的方法,方法准确、精密、简便,可望作为血清肌酐测定的参考方法.     

Liquid chromatography as candidate reference method for the determination of vitamins A and E in human serum

BackgroundOwing to the increasing interest in public health research of antioxidant micronutrients and the inaccuracy of routine serum concentrations of the fat‐soluble vitamins A (retinol) and E (DL‐α‐tocopherol) measurements, we developed a reliable, highly sensitive, robust and rapid method for the quantification of two clinically important lipophilic antioxidants in serum using a reverse‐phase HPLC/DAD method.MethodSample preparation and analytical conditions that would affect extraction efficiency and quantitative results of vitamins A and E were investigated and optimized. Vitamins A and E were extracted from serum via liquid‐liquid extraction (LLE). After adequate sample preparation, the samples were injected directly into the HPLC system with diode‐array detector (DAD). Chromatographic separation was completed in 7 minutes for vitamins A and E. With vitamin A acetate and vitamin E acetate as internal standards, the method was applied to the measurement of vitamins A and E in human serum.ResultsWe evaluated method linearity, accuracy (recovery rate and trueness), precision, carryover, limit of quantitation and limit of detection, and measurement uncertainty. The method was evaluated for trueness using NIST Standard Reference Material SRM 968f. The serum concentration of the studied compounds had a good linear relationship in the range of 0.05 ~ 3.0 μg/mL concentration (r ＝ 0.9998), with 0.0077 μg/mL detection limit and 0.025 μg/mL quantitative limit for vitamin A, respectively, and 1.0 ~ 60.0 μg/mL concentration (r ＝ 0.9999), with 0.40 μg/mL detection limit and 0.50 μg/mL quantitative limit for vitamin E, respectively. The intra‐ and inter‐assay coefficients of variation were calculated by using three concentrations (1, 2, and 3) of the studied compounds in human serum samples. Intra‐assay and inter‐assay precision were 1.23%‐4.97% and 0.97%‐3.79% for vitamin A, respectively, and 0.64%‐4.07% and 0.81%‐5.96% for vitamin E, respectively. The average recovery rates were 100.98% for vitamin A, and 99.21% for vitamin E, respectively. The carryover rate of vitamins A and E was below 1%. As for the evaluation of accuracy, the biases were <± 5% by comparing with NIST standard reference material SRM 968f.ConclusionThe method is a simple sample treatment procedure for the determination of fat‐soluble vitamins A and E in human serum with high sensitivity and specificity. The proposed method could be recommended as a candidate reference method for the determination of serum concentrations of the fat‐soluble vitamins A and E in human serum.     

A candidate reference method for coupled sodium-water determination in human serum

A candidate reference method is described for coupled sodium-water determination based on ion-exchange sodium separation from the serum matrix followed by gravimetry as Na2SO4, and serum water determination by means of microwave evaporation. For sera with normal sodium and water contents, the mean relative standard deviation is 0.6% (0.8 mmol/l). Mean inaccuracy for the coupled sodium-water determination is -0.3% (0.4 mmol/l). The candidate reference method can be considered a reference method because the reference method value did not differ significantly from the definitive value, there is no known source for interferences or bias, and misinterpretation due to abnormal protein or lipid levels is excluded because serum sodium is determined on a plasma water basis. Sodium concentrations determined by the candidate reference method are used for comparing field methods with the candidate reference method. If the resulting regression equation is used in the calibration procedure, good correlation between all (in)direct field methods and the candidate reference method is ensured, and accurate results are produced. Results of proficiency testing show a good correlation between (in)direct field methods and the candidate reference method, because sera with approximately normal water contents are used.     

反相高效液相色谱紫外法检测人血清尿酸

目的探讨日本临床化学会(JSCC)推荐的检测人血清尿酸(UA)的反相高效液相色谱紫外(HPLC-UV)法是否可作为候选参考方法来验证同位素稀释质谱法、评价常规方法。方法对反相HPLC-UV法进行复现并进行方法学评价。观察尿酸酶处理人血清样本后的色谱以评价其特异性;检测系列标准液的UA水平并绘制标准曲线,观察线性范围;用朗道公司质控品评价精密度;用UA标准液评价回收率;分别用有证参考物SRM 909b(Ⅰ和Ⅱ)、国家一级标准物质GBW 09176、GBW 09175、GBW 09174评价正确度,并与2008年国际临床化学与检验医学联合会(IFCC)参考实验室RELA(ring trials for reference labora-tories)结果进行比对;用改良Bland-Altman图评价5种常规检测系统与反相HPLC-UV法间的偏差。结果尿酸酶处理后UA色谱峰消失;本法的线性范围为2.08～1 785μmol/L;批内变异系数(CV)均<0.3%,批间CV均<0.4%,日间CV均<2.3%,总CV均<2.7%;平均相对回收率为96.0%～100.6%;与SRM909bⅠ和Ⅱ靶值的偏移分别为-2.5%、-2.3%;与GBW09176、GBW 09174、GBW 09175靶值的偏移分别为0.29%,-0.74%和0.06%;与参加RELA比对的另3家实验室的平均值进行比较,水平1偏移为0.35%,水平2为-0.69%;Hitachi、Beckman Coulter、Roche、Dade、Vitros常规检测系统检测人血清UA与反相HPLC-UA法的相关系数分别为0.998 9、0.996 5、0.999 2、0.999 2和0.998 7,与反相HPLC-UA法的偏差均小于5%的生物学变异。结论本法特异、简便、快速,精密度好,正确度高,与具有良好溯源的常规测定系统具有良好的相关性和一致性,可推荐作为人血清UA测定的候选参考方法。     

Deproteinizing methods evaluated for determination of uric acid in serum by reversed-phase liquid chromatography with ultraviolet detection

We evaluated six deproteinizing methods for determination of uric acid in serum by "high-performance" liquid chromatography with ultraviolet detection: those involving zinc hydroxide, sodium tungstate, trichloroacetic acid, perchloric acid, acetonitrile, and centrifugal ultrafiltration (with Amicon MPS-1 devices). We used a Toyosoda ODS-120A reversed-phase column. The mobile phase was sodium phosphate buffer (40 mmol/L, pH 2.2) containing 20 mL of methanol per liter. Absorbance of the eluate was monitored at 284 nm. The precipitation method with perchloric acid gave high recoveries of uric acid and good precision, and results agreed with those by the uricase-catalase method of Kageyama (Clin Chim Acta 1971;31:421-6).     

应用反相高效液相色谱内标法测定血清尿酸

目的 评价以5-氟尿嘧啶(5-FU)作内标的反相高效液相色谱(HPLC)测定血清尿酸(UA)的方法 ,拟初步推荐其作为血清UA测定的候选参考方法 ;并应用此方法 评价常规酶比色法测定血清UA的结果 偏倚.方法 对测定血清UA的反相HPLC内标法进行方法 学评价;通过测定有证参考物质(SRM)、参加国际临床化学与检验医学联合会(IFCC)参考实验室考察活动,验证此方法 的准确性及可靠性.以反相HPLC内标法为比较方法 ,以6种常用检测系统中的酶比色法作为实验方法 ,对61份血清样本进行测定.组成6个比对组,对每组比对数据作散点图、偏倚图,计算线性方程和相关系数(R2),进行偏倚评估.结果 反相HPLC内标法测定UA线性范围达1 190 μmol/L,批内变异系数(CV)＜2.1%,日间CV＜3.9%,绝对回收率为96.2%～101.0%,平均相对回收率为95.1%～99.4%.测定SRM的平均相对偏倚为-8.29%;测定IFCC参考实验室考察活动提供的样本,其结果 与同位素稀释质谱(ID-MS)法的相对偏倚范围为-3.45%～-1.26%;在Beckman、Roche、Dade、Vitros封闭系统及Beckman、Roche开放系统中的酶比色法分别与反相HPLC内标法比较,各组中2种方法 均相关良好(R2=0.996 9、0.997 2、0.995 2、0.996 7、0.997 3、0.994 7),在UA为120、470L、630 μmol/L时,预期相对偏倚范围分别为-14.6%～4.3%、-0.4%～8.0%、0.8%～8.8%,其中Beckman封闭系统测定结果 与反相HPLC内标法的一致性好,Roche封闭系统低值偏低,Dade和Vitros封闭系统高值偏高,封闭系统比开放系统结果 略好.结论 拟推荐以5-FU为内标的反相HPLC法作为血清UA测定的候选参考方法 .酶比色法在不同检测系统中所测结果 存在一些差异.     

应用反相高效液相色谱内标法测定血清尿酸

目的评价以5-氟尿嘧啶(5-FU)作内标的反相高效液相色谱(HPLC)测定血清尿酸(UA)的方法,拟初步推荐其作为血清UA测定的候选参考方法;并应用此方法评价常规酶比色法测定血清UA的结果偏倚。方法对测定血清UA的反相HPLC内标法进行方法学评价;通过测定有证参考物质(SRM)、参加国际临床化学与检验医学联合会(IFCC)参考实验室考察活动,验证此方法的准确性及可靠性。以反相HPLC内标法为比较方法,以6种常用检测系统中的酶比色法作为实验方法,对61份血清样本进行测定。组成6个比对组,对每组比对数据作散点图、偏倚图,计算线性方程和相关系数(R2),进行偏倚评估。结果反相HPLC内标法测定UA线性范围达1190μmol/L,批内变异系数(CV)<2.1%,日间CV<3.9%,绝对回收率为96.2%~101.0%,平均相对回收率为95.1%~99.4%。测定SRM的平均相对偏倚为-8.29%;测定IFCC参考实验室考察活动提供的样本,其结果与同位素稀释质谱(ID-MS)法的相对偏倚范围为-3.45%~-1.26%;在Beckman、Roche、Dade、Vitros封闭系统及Beckman、Roche开放系统中的...     

血清尿酸紫外分光光度参考方法的建立及性能评价

目的以尿酸酶紫外光度法为基础,建立血清中尿酸测定的参考方法并评价其性能.方法 用新鲜患者血清样本、迈瑞常规复合校准品等对方法的精密度进行评估;用有证参考物质SRM909bⅠ和Ⅱ、IFCC参考实验室质评样本Rela A/B对方法的准确度进行初步评价,同时测定新鲜人血清并与同位素稀释质谱法进行方法学对比,验证方法准确度.结果 方法对新鲜患者血清、厂家复合校准品等不同类型样本批内不精密度CVintra小于1%,总不精密度CVt小于2%;有证参考物质SRM909bⅠ/Ⅱ测定结果均在参考值范围内,对UA参考实验室能力验证样本Rela A/B测定结果与中心值结果相对偏差小于0.5%;血清样本测定结果与同位素稀释液相质谱法可比,线性回归斜率1.005,相关系数0.999,医学决定水平处引入的相对误差小于3.25%.结论 血清尿酸紫外分光光度法已基本建立,精密度和准确度符合要求,测量结果和同位素稀释液相色谱/质谱法可比,可为常规系统尿酸溯源体系的建立和性能评估提供便捷有效的方法.     

Determination of lipid hydroperoxides in serum iodometry and high performance liquid chromatography compared.

It is postulated that lipid peroxidation plays a role in the pathogenesis of a variety of diseases. Efforts have therefore been made to develop reliable and practicable procedures for quantifying lipid peroxidation products such as lipid hydroperoxides in biological specimens. An iodometric cholesterol colour reagent (Merck, Darmstadt, Germany) can be used to measure lipid hydroperoxides in isolated low density lipoproteins without lipid extraction. This method has been validated with respect to its analytical performance and suitability for serum samples by comparing it with a high performance liquid chromatography technique. The method was found to have acceptable performance characteristics with aqueous fatty acid hydroperoxide solutions (linoleic acid) and isolated low density lipoproteins, but it cannot be applied to native serum samples without extraction of lipids.     

高效液相色谱法测定人血清中褪黑素的浓度

目的用反相高效液相色谱法测定血清中褪黑素的含量。方法采用荧光检测器检测20例自愿者血清中的褪黑素。结果血清中褪黑素最低检测浓度为0.5pg·ml-1,检测限0.2pg,褪黑素在1.0～500pg·ml-1之间呈线性关系,回归方程Y=65744.7x-220.6(r=0.9989,P<0.05),回收率>94.7%,日间、日内变异系数均在10%以下。结论用反相高效液相色谱法测定血清中褪黑素的含量灵敏、快速、准确,为褪黑素在体内代谢等研究提供方法,对临床合理补充外源性褪黑素具有指导性。     

高效液相色谱法测定血清甘油三脂的研究

本文研究用高效液相色谱测定血清甘油三脂含量的方法。结果表明 ,用 1,2 ,4 丁三醇作内标 ,2 30nm为测定波长 ,在本文色谱条件下 ,测定血清甘油三脂的含量 ,其结果准确、灵敏、回收率高、操作较简便 ,是测定血清甘油三脂含量较理想的方法     

基于电感耦合等离子体质谱法血清钙离子检测候选参考方法的建立

目的基于电感耦合等离子体质谱法(ICP-MS),建立一种检测血清钙离子的候选参考方法。方法方法学建立.将从医院收集到的血清标本以0.3%硝酸溶液直接稀释100倍,在血清标本基质溶液中添加不同浓度钙标准溶液,配制含血清基质的标准品溶液。以锗(Ge)为内标,采用标准加入法,计算血清钙离子浓度。对所建立的候选参考方法进行线性、精密度、正确度的性能评估和方法比对。结果血清钙离子浓度在0.000~20.400 mmol/L内(稀释后浓度为0.000~0.204 mmol/L)线性良好(R2>0.9999);批内不精密度为0.22%~0.47%,批间不精密度为0.64%~0.77%,总不精密度为0.98%~1.09%;检测3个浓度SRM 956d,结果均在证书要求的不确定度范围内,相对偏移分别为-0.16%,0.04%,0.23%;该方法参加2017年参考实验室外部质量评价计划(RELA),比对通过。与检验医学溯源联合委员会(JCTLM)所列参考方法进行比较,结果一致性良好。本研究所建立的候选参考方法与临床常规电极方法进行比较,具有良好的相关性。结论成功建立血清钙离子检测候选参考方法,线性范围宽、具有良好的精密度与准确度。