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Find video protocols related to scientific articles indexed in Pubmed.
STANDARDISING CLINICAL MEASUREMENTS OF BACTERIA AND VIRUSES USING NUCLEIC ACID TESTS.
J. Clin. Microbiol.
PUBLISHED: 11-14-2014
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Nucleic acid based tests for infectious diseases currently used in the clinical laboratory and in point of care devices are diverse. Measurement challenges associated with standardisation of quantitative viral load testing are discussed in relation to human cytomegalovirus, BK and Epstein Barr virus, whilst the importance of defining the performance of qualitative methods is illustrated with Mycobacterium tuberculosis and Influenza virus. The development of certified reference materials of which values are traceable to higher order standards and reference measurement procedures, using for instance digital PCR, will further contribute to the understanding of analytical performance characteristics and promote clinical data comparability.
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A reference system for urinary albumin: current status.
Clin. Chem. Lab. Med.
PUBLISHED: 09-06-2013
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Increased urinary excretion of albumin reflects kidney damage and is a recognized risk factor for progression of renal and cardiovascular disease. Considerable inter-method differences have been reported for both albumin and creatinine measurement results, and therefore the albumin-to-creatinine ratio. Measurement accuracy is unknown and there are no independent reference measurement procedures for albumin and no reference materials for either measurand in urine.
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The importance of commutability of reference materials used as calibrators: the example of ceruloplasmin.
Clin. Chem.
PUBLISHED: 05-06-2013
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Different methods for ceruloplasmin tend to give different results in external quality assessment schemes. During the production of the certified reference material ERM-DA470k/IFCC discrepant measurement results were also found for ceruloplasmin measured with different methods, and consequently the protein could not be certified in the material.
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Gaps in the traceability chain of human growth hormone measurements.
Clin. Chem.
PUBLISHED: 03-21-2013
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Human growth hormone (hGH) is measured for the diagnosis of secretion disorders. These measurements fall under the EU Directive 98/79/EC on in vitro diagnostic medical devices requiring traceability of commercial calibrator values to higher-order reference materials or procedures (Off J Eur Communities 1998 Dec 7;L 331:1-37). External quality assessment schemes show large discrepancies between results from different methods, even though most methods provide results traceable to the recommended International Standard (IS 98/574). The aim of this study was to investigate possible causes for these discrepancies.
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Contributions of the EMERALD project to assessing and improving microarray data quality.
BioTechniques
PUBLISHED: 01-15-2011
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While minimum information about a microarray experiment (MIAME) standards have helped to increase the value of the microarray data deposited into public databases like ArrayExpress and Gene Expression Omnibus (GEO), limited means have been available to assess the quality of this data or to identify the procedures used to normalize and transform raw data. The EMERALD FP6 Coordination Action was designed to deliver approaches to assess and enhance the overall quality of microarray data and to disseminate these approaches to the microarray community through an extensive series of workshops, tutorials, and symposia. Tools were developed for assessing data quality and used to demonstrate how the removal of poor-quality data could improve the power of statistical analyses and facilitate analysis of multiple joint microarray data sets. These quality metrics tools have been disseminated through publications and through the software package arrayQualityMetrics. Within the framework provided by the Ontology of Biomedical Investigations, ontology was developed to describe data transformations, and software ontology was developed for gene expression analysis software. In addition, the consortium has advocated for the development and use of external reference standards in microarray hybridizations and created the Molecular Methods (MolMeth) database, which provides a central source for methods and protocols focusing on microarray-based technologies.
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Development of a candidate secondary reference procedure (immunoassay based measurement procedure of higher metrological order) for cardiac troponin I: I. Antibody characterization and preliminary validation.
Clin. Chem. Lab. Med.
PUBLISHED: 11-11-2010
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In this study, the first steps in the development of a secondary reference measurement procedure (RMP) higher metrological order measurement procedure to support the cardiac troponin I (cTnI) standardization initiative is described. The RMP should be used to assign values to serum-based secondary reference materials (RMs) without analytical artifacts causing bias. A multiplexed bead-based assay and sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) were used to identify the optimum monoclonal antibody pair (clones 560 and 19C7) for the RMP. Using these antibodies, an ELISA-based procedure was developed to accurately measure the main cTnI forms present in blood. The proposed RMP appears to show no bias when tested on samples containing various troponin complexes, phosphorylated and dephosphorylated forms, and heparin. The candidate assay displayed suitable linearity and sensitivity (limit of detection, 0.052 ?g/L) for the measurement of the proposed cTnI secondary RMs. Preliminary comparison data on patient samples with a commercial cTnI assay are also provided to support the suitability of RMP for value assignment to RMs. Full validation and final assessment of the RMP will be performed through transferability and inter-comparison studies.
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Nucleic acid reference materials (NARMs): definitions and issues.
Clin. Chem. Lab. Med.
PUBLISHED: 10-25-2010
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Molecular diagnostics is one of the most rapidly growing areas of laboratory medicine. This rapid growth of clinical molecular tests has outpaced the availability and development of reference methods and reference materials. Such methods and materials are important for the development, validation, and interpretation of diagnostic methods and tests. Yet, there is a lack of harmonization between the numerous international organizations currently either certifying or defining reference materials. The objective of this position paper is to review and clarify the definition, attributes and applications for the use of reference materials in the context of molecular diagnostics.
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Characterization of the new serum protein reference material ERM-DA470k/IFCC: value assignment by immunoassay.
Clin. Chem.
PUBLISHED: 10-05-2010
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The availability of a suitable matrix reference material is essential for standardization of the immunoassays used to measure serum proteins. The earlier serum protein reference material ERM-DA470 (previously called CRM470), certified in 1993, has led to a high degree of harmonization of the measurement results. A new serum protein material has now been prepared and its suitability in term of homogeneity and stability has been verified; after characterization, the material has been certified as ERM-DA470k/IFCC.
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Standardisation of cardiac troponin I measurement: past and present.
Pathology
PUBLISHED: 07-17-2010
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The laboratory measurement of cardiac troponin (cTn) concentration is a critical tool in the diagnosis of acute myocardial infarction (MI). Current cTnI assays produce different absolute troponin numbers and use different clinical cut-off values; hence cTnI values cannot be interchanged, with consequent confusion for clinicians. A recent Australian study compared patient results for seven cTnI assays and showed that between-method variation was approximately 2- to 5-fold. A major reason for poor method agreement is the lack of a suitable common reference material for the calibration of cTnI assays by manufacturers. Purified complexed troponin material lacks adequate commutability for all assays; hence a serum-based secondary reference material is required for cTnI with value assignment by a higher order reference measurement procedure. There is considerable debate about how best to achieve comparability of results for heterogeneous analytes such as cTnI, whether it should be via the harmonisation or the standardisation process. Whereas harmonisation depends upon consensus value assignment and uses those commercial methods which give the closest agreement at the time, standardisation comes closer to the true value through a reference measurement system that is based upon long-term calibration traceability. The current paper describes standardisation efforts by the International Federation of Clinical Chemistry and Laboratory Medicine Working Group on Standardization of cTnI (IFCC WG-TNI) to establish a reference immunoassay measurement procedure for cTnI of a higher order than current commercial immunoassay methods and a commutable secondary reference material for cTnI to which companies can reference their calibration materials.
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Analysis of the physicochemical state of C-reactive protein in different preparations including 2 certified reference materials.
Clin. Chem.
PUBLISHED: 07-12-2010
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Standardization of clinical measurements of C-reactive protein (CRP) is based on the availability of reference materials. The serum protein reference material ERM-DA470 was used as a calibrant for various commercially available immunoassays but has now been exhausted. The recently released ERM-DA470k/IFCC was intended to fully replace ERM-DA470. However, the new material was not suited for the certification of CRP because of a bias introduced by the lyophilization process that caused loss of about 20% of CRP measurable by routine immunoassays, compared with the nonlyophilized material that was stored in a liquid frozen state.
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Standardization of protein biomarker measurements: is it feasible?
Scand. J. Clin. Lab. Invest. Suppl.
PUBLISHED: 06-03-2010
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The standardisation of measurements of protein biomarkers, which are potentially heterogeneous in terms of fragmentation, modification, substitution, primary, secondary, tertiary and quaternary structure, is a demanding task. However, they are a prime target for standardisation efforts due to the importance of protein biomarkers in diagnostics and health care and the typically observed significant discrepancies in measurement results obtained with non-standardized platforms. Based on the experience gathered during successfully completed projects for the production of reference materials, pragmatic approaches are described how standardisation could become feasible despite the fuzziness of the target analytes.
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Assessment of commutability for candidate certified reference material ERM-BB130 "chloramphenicol in pork".
Anal Bioanal Chem
PUBLISHED: 06-01-2010
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Chloramphenicol (CAP), an effective antibiotic against many microorganisms, is meanwhile banned in the EU for treatment of food-producing animals due to adverse health effects. The Institute for Reference Materials and Measurements (IRMM) is currently developing a certified reference material (CRM) for CAP in pork, intended for validation and method performance verifications of analytical methods. The material will be certified using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and gas chromatography-mass spectrometry (GC-MS) methods and has a target CAP level around the minimum required performance limit (MRPL) of 0.3 microg/kg. To prove that the material can be applied as a quality control tool for screening methods, a commutability study was conducted, involving five commercially available enzyme-linked immunosorbent assay kits and one biosensor assay (BiaCore kit). Meat homogenates (cryo-milled wet tissue) with CAP concentrations around the MRPL and the candidate CRM (lyophilised powder) were measured by LC-MS/MS and GC-MS as well as the six screening methods. Pairwise method comparisons of results obtained for the two sample types showed that the CRM can successfully be applied as quality control (QC) sample to all six screening methods. The study suggests that ERM-BB130 is sufficiently commutable with the investigated assays and that laboratories applying one of the investigated kits therefore benefit from using ERM-BB130 to demonstrate the correctness of their results. However, differences among the assays were observed, either in the abundance of bias between screening and confirmatory LC and GC methods, the repeatability of test results, or goodness of fit between the methods.
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Traceability of values for catalytic activity concentration of enzymes: a Certified Reference Material for aspartate transaminase.
Clin. Chem. Lab. Med.
PUBLISHED: 05-06-2010
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A new reference material for the liver enzyme aspartate transaminase (AST) (L-aspartate: 2-oxoglutarate-aminotransferase, EC 2.6.1.1), also called aspartate aminotransferase (ASAT), has been developed under the code ERM-AD457/IFCC. This certified reference material (CRM) for AST has been produced from a human type recombinant AST expressed in Escherichia coli and a buffer containing bovine serum albumin, and has been lyophilised.
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Development and preparation of a new serum protein reference material: feasibility studies and processing.
Clin. Chem. Lab. Med.
PUBLISHED: 04-09-2010
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The availability of matrix reference materials is essential for the standardisation of (immuno)assays used to measure proteins. The reference material ERM-DA470 (previously called CRM470) certified in 1993 has led to a large degree of harmonisation of these assays. A new serum protein reference material has now been produced (ERM-DA470k). It is intended to replace ERM-DA470, and will additionally be certified for beta(2)-microglobulin (B2M).
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Considerations for the development of a reference method for sequencing of haploid DNA--an opinion paper on behalf of the IFCC Committee on Molecular Diagnostics, International Federation of Clinical Chemistry and Laboratory Medicine.
Clin. Chem. Lab. Med.
PUBLISHED: 10-13-2009
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Following the completion of sequencing of the human genome, there has been a very rapid increase in the development of new molecular diagnostic tests. However, the numerous genetic tests and genetic testing technologies offered do not always satisfy essential quality criteria required to ensure confidence in the results that are produced. This is of particular importance for genetic tests since many patients may be tested for a particular genetic defect only once in their lifetime. Thus, there is a pressing need for comprehensive guidelines for the validation of molecular diagnostic tests and procedures, including DNA sequencing, the latter being a fundamental aspect of the development and validation of most genetic tests. To that end, the International Federation of Clinical Chemistry and Laboratory Medicine (IFCC) Committee for Molecular Diagnostics has prepared the following paper that describes a possible approach to the development of a reference method for sequencing of haploid DNA. We discuss various aspects which should be considered before, during and after applying the sequencing procedure, in order to achieve results with a known level of confidence, including robustness and assessments of quality.
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Inter-laboratory assessment of PrPSc typing in creutzfeldt-jakob disease: a Western blot study within the NeuroPrion Consortium.
Brain Pathol.
PUBLISHED: 10-02-2009
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Molecular typing is of considerable importance for the surveillance and epidemiology of human transmissible spongiform encephalopathies (TSEs). It relies on the detection of distinct protease-resistant prion protein (PrP(Sc)) core fragments that differ in molecular mass and/or glycoform ratio. In this collaborative study, we tested the inter-laboratory agreement in TSE molecular typing. Sixteen characterized brain specimens from sporadic TSEs and variant Creutzfeldt-Jakob disease (vCJD) cases were distributed blindly to seven laboratories for molecular characterization by a defined protocol and classification. Agreement between laboratories in the classification of samples was excellent. In particular, there were no differences in the distinction between PrP(Sc) type 1, type 2A, and type 2B with one exception, which eventually was identified as a case with types 1 and 2 co-occurrence. This shows that the general technique and particular classification system used here are robust and represent a reliable basis for diagnostic and epidemiologic purposes. The subtle further distinction of subtypes among type 1 and type 2 groups requires high-sensitivity gel electrophoresis protocols that are unsuitable for routine diagnostic needs and must be reserved for research investigations. Further research is necessary on the identification and significance of co-occurrence of PrP(Sc) types 1 and 2 within one brain.
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Towards future reference systems for GM analysis.
Anal Bioanal Chem
PUBLISHED: 09-24-2009
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Despite the fact that the measurement unit for the quantification of GMOs in food and feed products has not yet been unambiguously agreed upon in Europe, international trade requires reliable GMO analysis measuring comparably the GMO content of products. The two reference systems, based either on mass fractions or on copy number ratios, and their metrological traceability chains are presented and discussed. It is concluded that, properly established and expressed, measurement results in copy number ratios can provide a metrologically sound reference system. In this case, certified reference materials used for calibration and quality control can be independent of each other and the uncertainty derived from calibration can correctly be included in the overall uncertainty of the GMO measurement. However, further efforts are required to establish this metrological system.
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Validation of a liquid chromatography-tandem mass spectrometry method for the identification and quantification of 5-nitroimidazole drugs and their corresponding hydroxy metabolites in lyophilised pork meat.
J Chromatogr A
PUBLISHED: 03-20-2009
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A liquid chromatography-electrospray ionisation tandem mass spectrometry method for the simultaneous detection and quantitation of 5-nitroimidazole veterinary drugs in lyophilised pork meat, the chosen format of a candidate certified reference material, has been developed and validated. Six analytes have been included in the scope of validation, i.e. dimetridazole (DMZ), metronidazole (MNZ), ronidazole (RNZ), hydroxymetronidazole (MNZOH), hydroxyipronidazole (IPZOH), and 2-hydroxymethyl-1-methyl-5-nitroimidazole (HMMNI). The analytes were extracted from the sample with ethyl acetate, chromatographically separated on a C(18) column, and finally identified and quantified by tandem mass spectrometry in the multiple reaction monitoring mode (MRM) using matrix-matched calibration and (2)H(3)-labelled analogues of the analytes (except for MNZOH, where [(2)H(3)]MNZ was used). The method was validated in accordance with Commission Decision 2002/657/EC, by determining selectivity, linearity, matrix effect, apparent recovery, repeatability and intermediate precision, decision limits and detection capabilities, robustness of sample preparation method, and stability of extracts. Recovery at 1 microg/kg level was at 100% (estimates in the range of 101-107%) for all analytes, repeatabilities and intermediate precisions at this level were in the range of 4-12% and 2-9%, respectively. Linearity of calibration curves in the working range 0.5-10 microg/kg was confirmed, with r values typically >0.99. Decision limits (CCalpha) and detection capabilities (CCbeta) according to ISO 11843-2 (calibration curve approach) were 0.29-0.44 and 0.36-0.54 microg/kg, respectively. The method reliably identifies and quantifies the selected nitroimidazoles in the reconstituted pork meat in the low and sub-microg/kg range and will be applied in an interlaboratory comparison for determining the mass fraction of the selected nitroimidazoles in the candidate reference material currently developed at IRMM.
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European external quality control study on the competence of laboratories to recognize rare sequence variants resulting in unusual genotyping results.
Clin. Chem.
PUBLISHED: 02-20-2009
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Depending on the method used, rare sequence variants adjacent to the single nucleotide polymorphism (SNP) of interest may cause unusual or erroneous genotyping results. Because such rare variants are known for many genes commonly tested in diagnostic laboratories, we organized a proficiency study to assess their influence on the accuracy of reported laboratory results.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.