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1.
One of the more frequent activities in health sciences is the measurement of biological quantities. Frequently, when reading biomedical books and journals some confusion on the metrological meaning of biological quantities related to the concepts ‘concentration’ and ‘content’ may be observed. Classically, a concentration is an amount of any type per volume of liquid or gas system, whereas content is an amount of any type per mass of liquid or gas or solid system. However the concepts ‘concentration’ and ‘content’ alone are still ambiguous because, depending on the type of amount of the component (analyte) per volume or mass of a system, there are different types of concentrations and contents. This article attempts to give a clarification of these concepts, mainly based on international recommendations about nomenclature and terminology of metrology, chemistry and clinical laboratory sciences.  相似文献   

2.
Errors in laboratory medicine occur in the preanalytical, analytical, and postanalytical phases. The errors are mostly detected in the preanalytical period. However, analytical errors are still an important source of error, despite their frequency is reduced significantly in years thanks to developments in laboratories. In this case, an analytical error was noticed during the verification of a patient’s results. The direct bilirubin of a 66-year-old male patient admitted to the emergency department was higher than the total bilirubin. The patient’s symptoms were fatigue and dyspnoea. Albumin and haemoglobin (Hb) concentrations of the patient were significantly low. After considering the patient’s demographics and laboratory results, the laboratory specialist suspected a paraproteinemia interference. Total protein was performed as a reflective test. The albumin/globulin ratio was reversed. Thereafter, serum protein electrophoresis (SPEP) and immunofixation electrophoresis (IFE) were performed as another reflective tests, respectively. SPEP and IFE results were in favour of monoclonal gammopathy. The patient was directed to a haematologist, underwent a bone marrow biopsy, and the result was reported as Waldenstrom’s macroglobulinemia with plasma cell differentiation expressing IgM-Kappa. The patient went on a chemotherapy protocol, and his condition has been improved in subsequent months. Detection of analytical errors is of great importance, like in our case, and may be used as a tool to identify patients who have not yet been diagnosed. The laboratory specialist must dominate the entire process of each test in the laboratory, be aware of the limitations of tests, and turn these disadvantages into advantages when necessary.  相似文献   

3.
This study considers the main challenges of presenting an iterative observer under a data-driven framework for nonlinear nonaffine multi-agent systems (MASs) that can estimate nonrepetitive uncertainties of initial states and disturbances by using the information from previous iterations. Consequently, an observer-based iterative learning control is proposed for the accurate consensus tracking. First, the dynamic effect of nonrepetitive initial states is transformed as a total disturbance of the linear data model which is developed to describe I/O iteration-dynamic relationship of nonlinear nonaffine MASs. Second, the measurement noises are considered as the main uncertainty of system output. Then, we present an iterative disturbance observer to estimate the total uncertainty caused by the nonrepetitive initial shifts and measurement noises together. Next, we further propose an observer-based switching iterative learning control (OBSILC) using the iterative disturbance observer to compensate the total uncertainty and an iterative parameter estimator to estimate unknown gradient parameters. The proposed OBSILC consists of two learning control algorithms and the only difference between the two is that an iteration-decrement factor is introduced in one of them to further reduce the effect of the total uncertainty. These two algorithms are switched to each other according to a preset error threshold. Theoretical results are demonstrated by the simulation study. The proposed OBSILC can reduce the influence of nonrepetitive initial values and measurement noises in the iterative learning control for MASs by only using I/O data.  相似文献   

4.
IntroductionIt is common for patients to switch between several healthcare providers. In this context, the long-term follow-up of medical conditions based on laboratory test results obtained from different laboratories is a challenge. The measurement uncertainty in an inter-laboratory context should also be considered in data mining research based on routine results from randomly selected laboratories. As a proof-of-concept study, we aimed at estimating the inter-laboratory reference change value (IL-RCV) for exemplary analytes from publicly available data on external quality assessment (EQA) and biological variation.Materials and methodsExternal quality assessment data of the Reference Institute for Bioanalytics (RfB, Bonn, Germany) for serum creatinine, calcium, aldosterone, PSA, and of whole blood HbA1c from campaigns sent out in 2019 were analysed. The median CVs of all EQA participants were calculated based on 8 samples from 4 EQA campaigns per analyte. Using intra-individual biological variation data from the EFLM database, positive and negative IL-RCV were estimated with a formula based on log transformation under the assumption that the analytes under examination have a skewed distribution.ResultsWe estimated IL-RCVs for all exemplary analytes, ranging from 13.3% to 203% for the positive IL-RCV and - 11.8% to - 67.0% for the negative IL-RCV (serum calcium - serum aldosterone), respectively.ConclusionExternal quality assessment data together with data on the biological variation – both freely available – allow the estimation of inter-laboratory RCVs. These differ substantially between different analytes and can help to assess the boundaries of interoperability in laboratory medicine.  相似文献   

5.
We describe a case of severe hypervitaminosis D and mild hypercalcaemia in a 68-year-old woman who presented with fatigue and weight loss. Her 25-hydroxy vitamin D (25OHD) was > 400 nmol/L (50-150) and corrected serum calcium was 2.83 mmol/L (2.1-2.6). Her intact parathyroid hormone (PTH) was 4.9 pmol/L (2.0-9.5). Further investigation revealed an IgM kappa paraprotein, and a bone marrow aspirate confirmed a diagnosis of lymphoplasmacytic lymphoma/Waldenstrom’s macroglobulinemia (LPL/WM). As the vitamin D level was discordant with the patient’s other results and presentation, the presence of an assay interferent was suspected. A 1-in-2 dilution of the sample returned a 25OHD result of 84 nmol/L in keeping with the presence of an interferent. Testing for rheumatoid factor was negative. The sample was treated with an antibody blocking reagent (Scantibodies) and results were not consistent with heterophile antibody interference. The sample was then analysed using liquid chromatography tandem mass spectrometry (LC-MS/MS), which returned a 25OHD result of 82 nmol/L. Testing on an alternative immunoassay platform produced a 25OHD result of 75 nmol/L. Reapeted testing on the original platform following reduction of the monoclonal paraprotein with chemotherapy, returned a result of 64 nmol/L. The patient’s mild hypercalcaemia persisted following resolution of the monoclonal paraprotein, in keeping with a diagnosis of primary hyperparathyroidism. This case highlights the potential for paraproteins to cause assay interference, and the importance of considering interference when results are incongruous with the clinical presentation.  相似文献   

6.
For state estimation of high accuracy, prior knowledge of measurement noise is necessary. In this paper, a method for solving the joint state estimation problem of jump Markov nonlinear systems (JMNSs) without knowing the measurement noise covariance is developed. By using the Inverse-Gamma distribution to describe the dynamics of measurement noise covariance, the joint conditional posterior distribution of the state variable and measurement noise covariance is approximated by a product of separable variational Bayesian (VB) marginals. In the newly constructed approach, the interacting multiple model (IMM) algorithm, as well as the particle-based approximation strategy, is employed to handle the computationally intractable problem and the nonlinear characteristics of systems, respectively. An interesting feature of the proposed method is that the distribution of states is spanned by a set of particles with weights, while the counterpart of measurement noise covariance is obtained analytically. Moreover, the number of particles is fixed under each mode, indicating a reasonable computational cost. Simulation results based on a numerical example and a tunnel diode circuit (TDC) system are presented to demonstrate that the proposed method can estimate the measurement noise covariance well and provide satisfied state estimation when the statistics of the measurement are unavailable.  相似文献   

7.

Introduction:

ISO 15189 was a new standard published in 2003 for accrediting medical laboratories. We believe that some requirements of the ISO 15189 standard are especially difficult to meet for majority of laboratories. The aim of this article was to present the frequency of nonconformities to requirements of the ISO 15189 accreditation standard, encountered during the assessments of medical laboratories in Hong Kong, during 2004 to 2009.

Materials and methods:

Nonconformities reported in assessments based on ISO 15189 were analyzed in two periods – from 2004 to 2006 and in 2009. They are categorized according to the ISO 15189 clause numbers. The performance of 27 laboratories initially assessed between 2004 and 2006 was compared to their performance in the second reassessment in 2009.

Results:

For management requirements, nonconformities were most frequently reported against quality management system, quality and technical records and document control; whereas for technical requirements, they were reported against examination procedures, equipment, and assuring quality of examination procedures. There was no major difference in types of common nonconformities reported in the two study periods. The total number of nonconformities reported in the second reassessment of 27 laboratories in 2009 was almost halved compared to their initial assessments. The number of significant nonconformities per laboratory significantly decreased (P = 0.023).

Conclusion:

Similar nonconformities were reported in the two study periods though the frequency encountered decreased. The significant decrease in number of significant nonconformities encountered in the same group of laboratories in the two periods substantiated that ISO15189 contributed to quality improvement of accredited laboratories.  相似文献   

8.
实验室在日常检测过程中,需要进行检测参数不确定度的评定,计算工作量大且较繁琐,通过使用Delphi 7开发测量不确定度分析软件,解决了测量不确定度的自动计算。本论文以实例展示了如何应用软件计算不确定度的计算过程。  相似文献   

9.
The practice of medical biochemistry in Slovenia includes clinical biochemistry (including toxicology, therapeutic drug monitoring, endocrinology, molecular diagnostics, immunology), hematology and coagulation. To start the vocational medical biochemistry training programme it's necessary to have a completed university degree (second cycle) in pharmacy, chemistry, biochemistry, medicine or other relevant university study and 1 year supervised practical training in medical laboratories, completed with mandatory state exam at Ministry of Health. The duration of vocational training programme is 4 years and is completed with final exam. The title after passed final examination is Medical biochemistry specialist. In October 2005 EC4 (Communities Confederation of Clinical Chemistry and Laboratory Medicine) approved Equivalence of standards of Slovenian national standards for medical biochemistry specialists. Since 2006 it is mandatory to be registered and to have valid license for medical biochemistry specialists and other professionals in laboratory medicine with at least university degree (second cycle) of education. Laboratory medicine in Slovenia is regulated globally through the Law of health-care activity and particularly through the Bylaw of laboratory medicine. The latter is based on standard ISO 15189, ratified in 2004. The Bylaw envisages granting working license to laboratories, valid for 5 years period. Granting of working licenses is ongoing process and first licenses have been granted in 2009. Important improvement toward the quality requirements for medical laboratories can be observed in the last 5 years. Parallel with the Bylaw of medical laboratories, Slovenian Accreditation (SA), the legal national accreditation body, started the initiative for accreditation of medical laboratories according to ISO 15189. It is in the implementation phase.  相似文献   

10.
To achieve accurate position control of electro-hydraulic asymmetric cylinder system with only available displacement signal, an output feedback controller is proposed in this paper. The dynamic model of the system is expressed as a Brunovsky form, which helps to estimate the system states and simplify the controller structure. Then Levant differentiator is introduced to estimate the position, velocity and acceleration of the asymmetric cylinder system based on the output signal, which can reduce the impact of measurement noise compared to the means of calculating the time derivative of the displacement signal directly. Besides, a high gain disturbance observer is designed to reject the lumped disturbance rejection of the system including parameter uncertainty, modelling error and external disturbance. Moreover, a sliding mode surface is introduced to the controller design and a robust item with continuous function is applied to compensate for estimation errors. According to Lyapunov theory, the developed output controller is pledged to be stable that can realize disturbance rejection control as well as backstepping-free control. Furthermore, a large-size asymmetric cylinder experimental rig is set up to simulate practical applications environment. Comparative experimental results reveal the validity and potential practical meaning of the developed control approach.  相似文献   

11.
IntroductionActivated partial thromboplastin time (aPTT) is determined and reported as clotting time in seconds aPTT(s), but it is presumed that reporting results as patient-to-normal clotting time ratio, aPTT(r), could minimize within-laboratory variability. The aim of study was to investigate differences in reporting aPTT results that can affect comparability of the results among Croatian laboratories and suggest further steps for its harmonization.Materials and methodsThe questionnaire on aPTT reporting practice was distributed to 83 laboratories through Survey Monkey application in March 2019 as the part of the first regular round of Croatian Centre for Quality Assessment in Laboratory Medicine proficiency testing.ResultsThe survey response rate was 0.49. Majority of laboratories report aPTT results as both, seconds and ratio. Participants reported use of 23 different aPTT(s) reference intervals along with 17 different combinations of reagent/coagulometer and 25 aPTT(s) denominators of different origin for aPTT(r) calculation. Despite the same aPTT(s) results, the use of different denominators caused a dispersion of aPTT(r) results that can lead to exceeding external quality assessment performance criteria of 7%, particularly when results were compared for the same reagent group only. By applying aPTT(s) reference interval mean as denominator for calculation of aPTT(r) reference interval better concordance to harmonized one was obtained (17 vs. 27; χ2 = 3.972; P = 0.046).ConclusionIn order to improve comparability of the results, laboratories are advised to use mean of aPTT(s) reference interval as denominator for aPTT(r) calculation. Type of coagulometer need to be considered when evaluating aPTT proficiency test results and its currently acceptable limit of performance evaluated accordingly.  相似文献   

12.
In a contemporary clinical laboratory it is very common to have to assess the agreement between two quantitative methods of measurement. The correct statistical approach to assess this degree of agreement is not obvious. Correlation and regression studies are frequently proposed. However, correlation studies the relationship between one variable and another, not the differences, and it is not recommended as a method for assessing the comparability between methods.
In 1983 Altman and Bland (B&A) proposed an alternative analysis, based on the quantification of the agreement between two quantitative measurements by studying the mean difference and constructing limits of agreement.
The B&A plot analysis is a simple way to evaluate a bias between the mean differences, and to estimate an agreement interval, within which 95% of the differences of the second method, compared to the first one, fall. Data can be analyzed both as unit differences plot and as percentage differences plot.
The B&A plot method only defines the intervals of agreements, it does not say whether those limits are acceptable or not. Acceptable limits must be defined a priori, based on clinical necessity, biological considerations or other goals.
The aim of this article is to provide guidance on the use and interpretation of Bland Altman analysis in method comparison studies.Key words: Bland-Altman, agreement analysis, laboratory research, method comparison, correlation of data  相似文献   

13.
单菁竹  李京梅  林雨霏  王国善 《资源科学》2018,40(10):1943-1953
选择实验法是通过问卷调查获取大量个体对资源环境属性状态选择集的偏好信息,评估资源环境非市场价值的前沿方法。受访者面对多种选择集的高信息负荷,由于认知水平受限,经常通过为物品属性设定可接受的最低/最高水平,即属性临界值,以简化决策过程,易造成模型估计结果的偏差。本文针对黄海胶州湾海域浒苔治理支付意愿,考虑属性临界值的存在及违反情况,设计引出属性临界值的选择实验问卷,建立修正选择模型,以青岛市实地调研的397个有效样本为数据来源,对居民浒苔治理意愿进行评估。研究结果表明：①属性临界值的存在及违反具有普遍性,忽略其存在及违反情况将导致估计结果的偏差;②将属性临界值存在及违反情况纳入效用方程,对传统选择实验分析框架进行修正,结果表明,经修正的选择模型的拟合度更优,能更好地解释受访者选择行为。在参数估计方面,浒苔治理恢复属性对居民效用水平显著正向影响,滨海景观、近海水质属性临界值的违反对居民效用水平显著负向影响;③青岛市居民对治理浒苔恢复滨海景观、改善近海水质、增加生物多样性和修复海洋生物资源的年支付意愿分别为90.68元、84.92元、49.34元、43.17元,2017年青岛市胶州湾海域浒苔治理总支付意愿为33.006亿元。与传统模型的对比表明,考虑属性临界值存在及违反情况的选择模型能更有效地反映受访者的实际边际效用,并在此基础上提高支付意愿估计结果的效度。  相似文献   

14.
本文利用非拓扑粒子模型计算了核物质环境中的核子(孤粒子)的尺度增量等物理量。这些结果可被认为是由核物质中真空性质的变化引起的。相对论性核平均场论可以用来研究核介质中与夸克相互作用的标量场。计算结果能够合理地符合与质量数相关的轻子与核的深度非弹散射的测量。  相似文献   

15.
苏红岩  王华 《资源科学》2019,41(12):2327-2341
对非市场物品和服务,如环境改善和资源保护,进行经济价值评估是学术界面临的一大难题。意愿调查法（Contingent Valuation Method, CVM）作为非市场物品经济价值评估的一种重要方法,其方法论在不断地接受检验并得到改进,近年来一个重要进展是其分析框架由确定偏好假设向不确定偏好假设转变。为系统认识国际上对CVM中受访者偏好不确定性的研究进展、推动国内相关研究,本文在简单介绍产生不确定结果的原因和不确定偏好假设下标准CVM不足的基础上,系统梳理了不确定偏好的测度方法和不确定偏好下价值计算方法,分析了各种方法的优劣以及考虑不确定性对价值估计值大小和估计效率的影响。总体来看,不确定偏好假设已基本形成共识,个人支付意愿应为随机变量也得到广泛支持。多数学者认为借助一定的测度技术获取的不确定性信息是有价值的,而如何更准确地测度和利用偏好不确定程度以提高资源环境等非市场物品价值估计效率应是今后研究的重点。最后,针对既有研究存在的问题,从加强个人偏好及不确定性的异质性研究、改进问卷设计等方面提出对未来研究工作的建议。  相似文献   

16.
Determination of blood glucose levels is very important to know the physiological condition of the human beings as the hormonal imbalance may cause abnormalities in glucose metabolism. The traditional methods of glucose estimation by colorimetric and titrimetric methods were involved with huge expenditure and time. The modified colorimetric microwell reader method proposed in the present study was performed with small quantities of sample and reagents with the same linearity that was observed in the normal colorimetric analysis. The modified method not only reduces the cost of the test to almost one third of the normal colorimetric method but also provide an opportunity to screen the large number of samples in a short duration of time.  相似文献   

17.
The tests currently employed within most haemostasis laboratories to monitor anticoagulant therapy largely comprise the prothrombin time (PT)/ International Normalised Ratio (INR) and the activated partial thromboplastin time (APTT). These are respectively used to monitor Vitamin K antagonists (VKAs) such as warfarin, and unfractionated heparin. Additional tests that laboratories may also employ for assessing or monitoring unfractionated heparin include thrombin time (TT) and the anti-Xa assay, which can also be used to monitor low molecular weight heparin. Several new anti-thrombotic agents have recently emerged, or are in the final process of clinical evaluation. These novel drugs that include Dabigatran etexilate and Rivaroxaban would not theoretically require monitoring; however, testing is useful in specific situations. The tests currently used to monitor VKAs and heparin are typically either too sensitive or too insensitive to the new drugs to be used as ‘typically performed in laboratories’, and may thus require some methodological adjustments to increase or decrease their sensitivity. Alternately, different tests may be better employed in these assessments. Whatever the case, laboratories may soon be performing a reduced or possibly increased number of tests, the same kind of tests but perhaps differently, or conceivably different assay panels. Specific laboratory guidance on the choice of the appropriate test to be ordered according to the drug being administered, as well as on appropriate interpretation of test results, will also be necessary. The current report reviews the current state of play and provides a glimpse to the possible future of the coagulation laboratory.  相似文献   

18.

Introduction

To investigate the state of the art of intra-laboratory turnaround time (intra-TAT), provide suggestions and find out whether laboratories accredited by International Organization for Standardization (ISO) 15189 or College of American Pathologists (CAP) will show better performance on intra-TAT than non-accredited ones.

Materials and methods

479 Chinese clinical laboratories participating in the external quality assessment programs of chemistry, blood gas, and haematology tests organized by the National Centre for Clinical Laboratories in China were included in our study. General information and the median of intra-TAT of routine and stat tests in last one week were asked in the questionnaires.

Results

The response rate of clinical biochemistry, blood gas, and haematology testing were 36% (479 / 1307), 38% (228 / 598), and 36% (449 / 1250), respectively. More than 50% of laboratories indicated that they had set up intra-TAT median goals and almost 60% of laboratories declared they had monitored intra-TAT generally for every analyte they performed. Among all analytes we investigated, the intra-TAT of haematology analytes was shorter than biochemistry while the intra-TAT of blood gas analytes was the shortest. There were significant differences between median intra-TAT on different days of the week for routine tests. However, there were no significant differences in median intra-TAT reported by accredited laboratories and non-accredited laboratories.

Conclusions

Many laboratories in China are aware of intra-TAT control and are making effort to reach the target. There is still space for improvement. Accredited laboratories have better status on intra-TAT monitoring and target setting than the non-accredited, but there are no significant differences in median intra-TAT reported by them.Key words: quality indicators, quality control, clinical laboratory services  相似文献   

19.
External Quality Assessment Scheme (EQAS) involves evaluation of a number of laboratories by an outside agency on the performance of a number of laboratories based on their analytical performance of tests on samples supplied by the external agency. In developing countries, establishment of national EQAS by preparing homemade quality control material is a useful scheme in terms of resources and time to monitor the laboratory performance. The objective of this study is to implement an EQAS to monitor the analytical performance of the district laboratories in Bhutan. Baseline information was collected through questionnaires. Lyophilized human serum including normal and abnormal levels were prepared and distributed to 19 participating laboratories. Nine routine analytes were included for the study. Their results were evaluated using Variance index scores (VIS) and Coefficient of variations (CV) was compared with Clinical Laboratory Improvement Act (CLIA) Proficiency Testing Criteria (PT) for each analyte. There was significant decrease in CV at the end of the study. The percentages of results in acceptable VIS as ‘A’ were 63, 60, 66, 69, 73 and 74, 75, 76 and 79 % in November 2009–July 2010 respectively. From our results, we concluded that, establishment of EQAS through distribution of home-made quality control material could be the useful scheme to monitor the laboratory performance in clinical chemistry in Bhutan.  相似文献   

20.

Introduction

Technological innovation requires the laboratories to ensure that modifications or incorporations of new techniques do not alter the quality of their results. In an ISO 15189 accredited laboratory, flexible scope accreditation facilitates the inclusion of these changes prior to accreditation body evaluation. A strategy to perform the validation of a biochemistry analyzer in an accredited laboratory having a flexible scope is shown.

Materials and methods:

A validation procedure including the evaluation of imprecision and bias of two Dimension Vista analysers 1500 was conducted. Comparability of patient results between one of them and the lately replaced Dimension RxL Max was evaluated. All studies followed the respective Clinical and Laboratory Standards Institute (CLSI) protocols. 30 chemistry assays were studied. Coefficients of variation, percent bias and total error were calculated for all tests and biological variation was considered as acceptance criteria. Quality control material and patient samples were used as test materials. Interchangeability of the results was established by processing forty patients’ samples in both devices.

Results:

27 of the 30 studied parameters met allowable performance criteria. Sodium, chloride and magnesium did not fulfil acceptance criteria. Evidence of interchangeability of patient results was obtained for all parameters except magnesium, NT-proBNP, cTroponin I and C-reactive protein.

Conclusions:

A laboratory having a well structured and documented validation procedure can opt to get a flexible scope of accreditation. In addition, performing these activities prior to use on patient samples may evidence technical issues which must be corrected to minimize their impact on patient results.  相似文献   

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