游离前列腺特异性抗原性能指标的建立

目的建立Axceed 260磁微粒全自动化学发光免疫分析仪检测游离前列腺特异性抗原(f-PSA)的空白限(LoB)、最低检出限(LoD)及定量检出限(LoQ)。方法参照美国临床实验室标准化协会2012年颁发的EP17-A2《临床实验室评价检测能力(第2版)》,将f-PSA的空白样品及系列低浓度样品在Axceed 260磁微粒全自动化学发光免疫分析系统进行检测,根据数据的分布规律,采用相应的统计学方法,确定该方法检测f-PSA的LoB、LoD及LoQ。结果 f-PSA的LoB为0.05ng/mL,LoD为0.16ng/mL,LoQ为0.35ng/mL。结论建立的Axceed 260磁微粒全自动化学发光免疫分析系统f-PSA的LoB、LoD、LoQ,其检测能力符合临床检验要求。     

化学发光免疫法检测AFP的空白限、检出限和定量检测限的建立与评价

目的 建立并评价化学发光免疫法检测甲胎蛋白（AFP）的空白限（LoB）、检出限（LoD）和定量检测限（LoQ）。 方法 参考CLSI EP17-A文件,将AFP空白样品和系列低浓度样品在Bayer Centaur 240化学发光免疫检测系统上进行检测,依据数据的分布规律,采用相应的统计学方法,确定血清AFP的LoB、LoD和LoQ,同时用传统方法建立AFP的检测低限(LLD)、生物检测限(BLD)和功能灵敏度(FS)。 结果 用EP17-A方案建立的LoB为0.80 ng/ml,LoD为2.60 ng/ml,LoQ为3.30 ng/ml;应用常规方法建立的LLD为1.00 ng/ml,BLD为2.20 ng/ml,FS为2.20 ng/ml。 结论 应用两种方法建立的LoB和LLD均低于仪器说明书声明的灵敏度性能,Bayer Centaur 240化学发光免疫系统检测AFP的分析灵敏度得到验证确认;实验室在验证仪器声明的LoB时,应同时建立检测系统的LoD和LoQ,以便为临床提供更为可靠的检验结果。两种评价方案均具有实用性,国内实验室可视具体情况选择不同的评价方案。     

电化学发光免疫法检测降钙素原的空白限、检出限和功能灵敏度的评价

目的对Roche Cobas E601全自动电化学发光免疫检测系统检测降钙素原(PCT)的检测限值和功能灵敏度(FS)进行评价。方法参照美国临床和实验室标准化协会(CLSI)EP-17A文件,将空白样品生理盐水及系列低浓度样品在Roche Cobas E601全自动电化学发光免疫检测系统进行检测,确定该方法的空白限(LoB),检出限(LoD)和FS。结果 PCT的LoB为0.029ng/mL,LoD为0.068ng/mL,FS为0.034ng/mL。结论建立了Roche Cobas E601全自动电化学发光仪PCT的LoB,LoD和FS,其分析灵敏度性能指标符合厂商提供的性能指标。为临床诊断和治疗提供了更有价值的信息。     

吡喃糖氧化酶法检测1,5-脱水葡萄糖醇的空白限、检出限和功能灵敏度的建立及评价

目的建立吡喃糖氧化酶法检测1,5-脱水葡萄糖醇(1,5-AG)的空白限(LoB)、检出限(LoD)和功能灵敏度(FS)并进行评价。方法参考美国临床和实验室标准化委员会(NCCLS)发布的EP17-A文件,将1,5-AG空白标本和系列低水平标本在ADVIA2400生化分析仪上测定1,5-AG,确定该方法的LoB、LoD和FS。结果依据NCCLS EP17-A方案建立吡喃糖氧化酶法检测1,5-AG的LoB为0.35μg/mL,LoD为0.64μg/mL,FS为0.960μg/mL。结论该研究建立了适合实验室ADVIA2400生化分析仪吡喃糖氧化酶法检测1,5-AG的LoB、LoD和FS,其分析性能指标基本满足实验室的要求,可为临床提供准确、可靠的检验结果。     

时间分辨荧光分析法检测低值乙型肝炎病毒表面抗原的质量评价

目的评价时间分辨荧光分析法检测低值乙型肝炎病毒表面抗原（HBsAg）的性能。方法使用不同浓度试剂盒标准品、二级标准品进行重复测定,建立相应的数学模型,进行检测低限（lower limit of detection,LLD）、生物检测限（biologic limit of detection,BLD）、功能灵敏度（functional sensitivity,FS）、空白限（limit of blank,LoB）、检出限（limit of detection,LoD）、定量检出限（limit of quantifications,LoQ）的统计计算。结果 LLD为0.044ng/mL、BLD为0.18ng/mL、FS为0.18ng/mL、LoB为0.03ng/mL、LoD为0.108ng/mL,尝试计算低值HBsAg检测结果的不确定度,确定定量检出限（LoQ）约为0.5ng/mL。结论使用灵敏度性能和不确定度2种方法进行评价,该检测系统对低值HBsAg分析能够达到试剂盒规定的性能要求。     

前清蛋白定量检测限和功能灵敏度的评价及临床应用

目的：对 Roche Modular P 全自动生化分析仪检测前清蛋白（PA）的空白限（LoB）、检测限（LoD）、定量检测限（LoQ）以及功能灵敏度（FS）进行评价。方法参照美国临床和实验室标准化协会（CLSI）EP-17A 文件,将空白样品生理盐水及系列低浓度样品在 Roche Modular P 全自动生化分析仪上进行检测确定该方法的空白限、检出限和定量检测限。依据国内通用方法确定功能灵敏度。结果 PA 的空白限为16．35 mg/L ,检测限为18．23 mg/L ,定量检测限暂无法评价,功能灵敏度为25．00 mg/L。结合其可报告范围的低值,确定其临床的报告范围及报告方式。结论建立了 PA 在 Roche Modular P 全自动生化分析仪上检测的定量检测限,为临床诊断和治疗提供了更有价值的信息,对不同评价的方法进行比较,明确了不同方法实际应用的优点以及局限性。     

化学发光免疫法检测B型利钠肽的检测限值和功能灵敏度研究

目的 探讨西门子ADVIA Centaur 240化学发光免疫系统检测B型利钠肽(BNP)的检测限值和功能灵敏度.方法 参照美国临床实验室标准化协会(CLSI)EP-17A文件和有关文献,选择BNP通用稀释液作为空白标本,批内重复测定10次,计算光量子值的均数、标准差和变异系数(CV),用以确定检测低限(LLD);同时,空白标本每天上、下午各检测1批,每批重复检测3次,连续检测5 d,共获得30个空白结果,用非参数方法确定空白限(LoB).制备接近1～4倍LoB浓度的系列实验标本,各浓度每天上、下午各检测1次,连续检测5 d,计算每个浓度水平光量子值的均数、标准差和CV,用以确定生物检测限(BLD)和CV值为10%条件下的功能灵敏度(FS);同时对所有80个测定结果,按EP-17A文件采用非参数方法确定检出限(LoD).结果 ADVIA Centaur 240检测系统BNP的LLD为1.47 pg/mL,LoB为0.86 pg/mL,均低于厂家声明的灵敏度;BLD为3.27～3.71 pg/mL,LoD为3.54 pg/mL,10%CV条件下的FS为4.64 pg/mL.结论厂商声明的LLD和BLD得到验证,同时建立了实验室BNP检测的LoB、LoD和FS,为临床提供了准确、可靠的检验结果.建议临床实验室使用EP-17A文件确定LoB和LoD,并确定在一定精密度条件下的FS.     

化学发光法测定anti-HBs的检出限和临床可报告范围的建立及临床应用

目的建立化学发光法测定anti-HBs的检出限和临床可报告范围,并进行临床应用评价。方法依据相关文件,设计化学发光法测定anti-HBs的空白限(LoB)、检出限(LoD)、定量检出限(LoQ)、分析测量范围(AMR)、临床可报告范围(CRR)的方案,并进行测量;应用建立的临床可报告范围和最大稀释度对急性乙肝患者恢复期进行预测及2016年1～6月期间出生的51例新生儿不同疫苗接种效果的评价。结果化学发光法测定anti-HBs的LoB,LoD,LoQ,AMR和CRR分别为0.87,1.89,3.0,0～970.50,3.0～48 525 mIU/ml,且最大稀释度为1:50;急性乙肝患者在就诊后第4周anti-HBs就出现升高(临床可报告范围),三种疫苗接种后的anti-HBs均值以B疫苗最高。结论化学发光法测定anti-HBs的检出限和临床可报告范围的建立能满足临床实验室的要求,为临床提供可靠的检验结果。     

肌氨酸氧化酶法检测尿肌氨酸的方法学性能评价及参考值分析

目的对肌氨酸氧化酶法检测尿肌氨酸进行方法学性能评价,初步估计尿肌氨酸的生物参考值。方法参考CLSI EP5-A2、EP17-A、EP6-A、C28-A3等文件,评价肌氨酸氧化酶法检测尿肌氨酸的重复性、空白限(limits of blank,LoB)、检测限(limitsof detection,LoD)、定量限(limits of quantitation,LoQ)、线性范围、回收率和生物参考值。结果肌氨酸氧化酶法检测2.0μmol/L肌氨酸溶液、2.9μmol/L新鲜尿液样本,总不精密度均14.0%;肌氨酸氧化酶法检测5.0、10.0μmol/L肌氨酸溶液及6.4、9.8μmol/L新鲜尿液样本,总不精密度均10.0%。肌氨酸氧化酶法检测尿肌氨酸的LoB约为0.35μmol/L;肌氨酸溶液的LoD、LoQ分别为1.1、1.9μmol/L,新鲜尿样本分别为1.2、2.0μmol/L;线性范围为2.0～125.6μmol/L;回收率为65.3%～90.5%。健康人群尿肌氨酸的生物参考值为0.01～0.06μmol/g肌酐。结论肌氨酸氧化酶方法检测尿肌氨酸的精密度、检测限、线性范围等可满足临床实验室的要求,但仍需在校准品基质方面有所改进以提高准确度。     

卫生行业与医药行业相关标准检出限的异同解析

当体外诊断试剂厂商仅按医药行业标准对某个定性检测项目声明了空白限(LoB)时,临床实验室应完成该项目检出限(LoD)的性能验证。文章对多个医学相关个行业标准中LoD、LoB的定义进行分析,并指出其在各文件中的异同。同时将定性项目中C50浓度、C95浓度与定量项目中LoD、LoB的相互联系进行归纳、整理。     

Partly nonparametric approach for determining the limit of detection

BACKGROUND: According to recent International Organization for Standardization (ISO) standards, the limit of detection (LoD) of an assay should be estimated taking both type I (alpha) and II (beta) errors into account. The suggested procedure, however, supposes gaussian distributions of both blank and sample measurements and a linear calibration curve. In clinical chemistry, asymmetric, nongaussian blank distributions are common, and the calibration curve may be nonlinear. We present a partly nonparametric procedure that takes these aspects into account. METHODS: Using theoretical distribution models and simulation studies, we developed a LoD estimation procedure suitable for the field of clinical chemistry that is partly based on nonparametric statistics. RESULTS: For sample size n, the nonparametrically determined 95th percentile of the blank measurements obtained as the value of the [n(95/100) + 0.5]th ordered observation defines the limit for results significantly exceeding zero [limit of blank (LoB)]. The LoD is the lowest value that is likely to yield a result exceeding the LoB. LoD is estimated as: LoB + cbeta x SDS, where SDS is the analytical SD of a sample with a low concentration; cbeta = z(1 - beta)/[1 - 1/(4 x f)]; z(1 - beta) is the standard normal deviate; and f is the number of degrees of freedom for estimation of SD(S). c(beta) is approximately equal to 1.65 for a type II error of 5%. Approaches and needed tabular values for calculation of confidence limits are presented as well as sample size. Worked examples are given to illustrate estimation and verification of the limit of detection. Simulation results are used to document performance. CONCLUSION: The proposed procedure appears useful for application in the field of clinical chemistry and promotes a standardized approach for estimating LoDs of clinical chemistry assays.     

Experimental optimization of the detection limit of two-step solid-phase radioimmunoassay

For two-step inhibition radioimmunoassay (sequential saturation or delayed addition of labeled antigen) generally a higher sensitivity than for one-step inhibition radioimmunoassay (equilibrium assay) is expected. The detection limit of a two-step solid phase inhibition radioimmunoassay for human serum immunoglobulin. A was minimized by statistical methods of experimental optimization. Under optimal conditions the detection limit was 2.3 ng IgA. This is about 1.8 times lower than the minimal detection limit of the one-step assay under similar conditions of the qualitative variables such as the origin of the antibody. This increase in sensitivity was associated with a decrease in the precision of the assay. The results are discussed with respect to the comparison of the one-step and the two-step assay and the usefulness of a sensitive radioimmunoassay in practice.     

Experimental optimization of the detection limit of one-step solid-phase radioimmunoassay

The minimal detection limit and the conditions of maximal sensitivity of a one-step solid-phase inhibition radioimmunoassay for human immunoglobulin A have been determined by application of statistical methods of experimental optimization. The choice of the optimal combination of qualitative variables, such as the origin of the antibody and the nature of the solid phase, was made by the study of a covariable under non-optimal conditions of the quantitative variables, such as the amount of antibody. The covariable was the avidity of the antibody, which is expected to have a large influence on the sensitivity. Only the difference in avidity between two immunosorbents with cellulose or Sepharose as solid-phase material proved to be statistically significant, and further study was done with cellulose. The experimental optimization of the sensitivity as a function of five quantitative variables yielded a reduction of the detection limit by a factor 5.6 (from 23.5 to 4.2 ng IgA). The variables determining the amount of insolubilized antibody in the assay had the largest influence on the value of the detection limit. The conditions of optimal sensitivity did agree with the predictions by a physical model of radioimmunoassay. The results are discussed in relation to the assay parameters such as the amount and the avidity of the insolubilized antibody and the initial percentage of binding, and in relation with theoretical optimization of the sensitivity.     

HBV—DNA荧光定量PCR检测下限的确立

目的 确立本实验室荧光定量PCR检测HBV-DNA项目的检测下限.方法 分别测定原倍HBV-DNA质控血清及经100、200倍稀释后HBV-DNA含量.结果 原倍质控血清测定结果的均值为3.63×104 IU/mL（4.56）,在给定靶值范围2.14×104～2.14×105 IU/mL（4.33～5.33）的低值附近;100倍稀释后的检测结果的均值为3.32 × 102 IU/mL（2.52）,在试剂盒最低检测下限（500 IU/mL）以下,且100份标本能100%定量检测.结论 本实验室设备及所用的试剂、方法对HBV-DNA〉500 IU/mL的标本完全有能力定量检测;检测下限为500 IU/mL是符合要求的.     

Relationship between detection limit and bias of accuracy of quantification of RNA by RT-PCR

Evidence is presented demonstrating that the distribution of data obtained applying a given RT-PCR method deviates from a normal distribution depending on the limit of detection. The effect of this is a bias towards higher values and concomitantly a systematic error in respect to the accuracy of the evaluation due to this deviation from normality. In addition, evidence is presented that an evaluation assuming a log-normal distribution is more appropriate.     

Effect of sample aliquot size on the limit of detection and reproducibility of clinical assays

BACKGROUND: Nucleic acid amplification technologies significantly improved the limit of detection (LOD) for diagnostic assays. The ability of these assays to amplify fewer than 10 target copies of DNA or RNA imposes new requirements on the preparation of clinical samples. We report a statistical method to determine how large of an aliquot is necessary to reproducibly provide a detectable number of cells. METHODS: We determined the success probability (p) based on aliquot size and sample volume. The binomial distribution, based on p and the concentration of cells in sample, was used to calculate the probability of getting no target objects in an aliquot and to determine the minimum number of objects per aliquot necessary to generate a reproducible clinical assay. RESULTS: The described method was applied to find a minimum aliquot volume required for a set LOD, false-negative rate (FNR), and %CV. For example, to keep FNR <0.01% for 0.5%, 1% and 2% aliquots (minimum 2000, 1000, and 500 cells per sample) are required. Comparison between experimental and predicted FNR demonstrated good correlation for the small volume aliquots and/or low concentration of target. When 4 muL of 200 copies/mL of plasmid is amplified, predicted and experimental FNRs are 47.2% and 44.9%. CONCLUSION: This probability model is a useful tool to predict the impact of aliquot volume on the LOD and reproducibility of clinical assays. Even for samples for which pathogens are homogeneously distributed, it is theoretically impossible to collect a single pathogen consistently if the concentration of pathogen is below a certain limit.     

时间分辨荧光法检测乙型肝炎病毒血清标志物的检出限探讨

目的确立时间分辨荧光方法检测血清乙型肝炎病毒(乙肝)表面抗原(HBsAg)、乙肝表面抗体(HBsAb)、乙肝e抗原(HBeAg)、乙肝e抗体(HBeAb)以及乙肝核心抗体(HBcAb)(俗称乙肝两对半)的检出限(LOD),以指导其检测结果的合理解释与应用。方法参考美国临床检验标准化委员会(CLSI)EP17-A文件提供的方案和相关文献,建立实验室时间分辨荧光分析仪检测血清乙肝两对半的空白限(LOB)及LOD。结果时间分辨荧光分析仪检测血清乙肝两对半中HBsAg、HBsAb、HBeAg、HBeAb、HBcAb的LOB分别为0.042 5ng/mL、0.500 5mIU/mL、0.000PEIU/mL、0.997DRU/mL、0.091DRU/mL;LOD分别为0.163ng/mL、1.203 mIU/mL、0.401PEIU/mL、1.756DRU/mL、0.350DRU/mL。结论时间分辨荧光方法检测血清乙肝两对半,均有较低的检出限,可较敏感地检出血清乙肝两对半中的各项抗原及抗体,早期指导临床对乙型肝炎病毒感染的诊断、疗效的观察及预后的判断。     

Authorized SARS-CoV-2 molecular methods show wide variability in the limit of detection.

On February 29^th, 2020, the U.S. Food and Drug Administration issued the first Emergency Use Authorization (EUA) for a SARS-CoV-2 assay outside of the U.S. Centers for Disease Control and Prevention. As of May 3^rd, 2021, 289 total EUAs have been granted. Like influenza, there is no standard for defining limit of detection (LoD), but rather guidance that analytical sensitivity/LoD be established as the level that gives a 95% detection rate in at least 20 replicates. Here we compare the performance characteristics of SARS-CoV-2 tests receiving EUA by standardizing sensitivity to a common unit of measure and assess the variability in LoD between tests. Additionally, we looked at factors that may impact sensitivities due to lack of standardization of the test development process and compare results for a standardized reference panel for comparative analysis within a subset of EUA tests offered by the U.S. Food and Drug Administration.