Forgot your password?
New user?
New Window Opens on the Secret Life of Microbes: Scientists Develop First Microbial Profiles of Ecosystems
CAS announces the release of SciFinder Scholar for Mac OS X
Press Releases
Press Releases
| Check out our New Publishers' Select for Free Articles |
Accreditation and Quality Assurance: Journal for Quality, Comparability and Reliability in Chemical Measurement (v.9, #11-12)
Impact of international standards and initiatives on proficiency testing for medical laboratories by Daniel W. Tholen (pp. 653-656).
This paper is intended to briefly discuss several recent initiatives regarding External Quality Assessment (or Proficiency Testing) (PT/EQA) for medical laboratories in various parts of the world. While a brief paper cannot be comprehensive for all regions, it is possible to present some new standards and initiatives that are underway or proposed in many countries. Laboratory medicine was one of the first areas of laboratory testing to develop interlaboratory comparisons, and the first area where such comparisons became compulsory. Because of that, the medical field has often been the leader in the availability and use of PT/EQA, and has introduced many innovations that have been adopted in other areas. Perhaps other areas of testing will similarly adopt the developments discussed here, if they have not already done so. There are important developments in the medical area that are also occurring in other fields of testing, such as the growing number of countries that require some form of participation, and the increasing use of the Internet. These developments are important, but are not discussed further in this paper since they are occurring in many fields of testing.
Harmonisation of proficiency testing schemes by Adriaan M. H. van der Veen; Theo L. Hafkenscheid (pp. 657-661).
The harmonisation of proficiency testing (PT) schemes has been under debate for a long time. There are obvious reasons why harmonisation of the practices in PT would be beneficial. In many areas, there is still a belief that further harmonisation of practices in PT would improve the comparability of measurement data. In particular when two laboratories are to be compared that have not participated in a single PT, problems arise which allegedly can be overcome by further harmonisation of PT schemes. In practice, however, parties involved in PT are not always embracing the idea of harmonisation. With the results of two European projects in mind, a discussion is given on harmonisation aspects, and some considerations are given that may help to decide in practice whether harmonisation is likely to solve particular problems. The first project, the European Proficiency Testing Network (EPTN), is concerned with further harmonisation. The second European project (COEPT) aims at providing a basis to assess equivalence across proficiency tests, and explores the conditions under which such an assessment is feasible.
Keywords: Proficiency testing; Harmonisation; Standardisation; Statistics; Equivalence
Bioterrorism: impact on external quality assessment service delivery by Christine Walton (pp. 662-665).
Safety issues related to the design, production and distribution of simulated specimens for microbiology external quality assessment (EQA) have occupied scheme organisers for many years. Since the anthrax attacks in Washington, USA in October 2001, there has been heightened awareness in the public domain regarding the transport of infectious substances. For instance, in direct response to the anthrax incident in the US, microbiology institutes in the UK that handle dangerous pathogens (like the Health Protection Agency) are registered with the national police force and are inspected regularly to ensure compliance with current legislation covering the control of these pathogens. The fear of a complete ban on the movement of infectious substances following the anthrax incident has not yet been realised, but remains a serious risk. Many countries such as the UK, USA, and Australia have introduced measures for the control, transportation, and health and safety aspects of handling and distribution of infectious materials. The national postal services of many countries do not accept infectious materials by mail. There are a limited number of courier services willing to transport dangerous goods, especially division 6.2 (infectious substances) and these services are costly. Measures can be implemented by scheme organisers to ensure best practice; for instance, by having sufficient and trained staff, with knowledge, expertise and use of computerised systems in the shipping/export department. Ensuring compliance with national and international health and safety legislation by providing safety data sheets and by carrying out product risk assessments is required to ensure transparency and to demonstrate duty of care. Organisers of microbiology EQA face uncertainty about the future survival of schemes in the current climate. It is imperative that practices and procedures are put into place that meet with the legislation and enable us to continue to support quality in laboratory medicine.
Keywords: Bioterrorism; EQA; Microbiology
Introduction of measurement uncertainty estimation into analytical instrument software: mission impossible? by Signe Leito; Ivo Leito (pp. 666-670).
In this paper we argue that introduction of ISO GUM based uncertainty estimation into analytical equipment software is a “mission possible” and is wholly realistic at this stage of development of the art. A possible general scheme of implementation of uncertainty estimation into analytical instrument software is presented based on the example of high-performance liquid chromatography (HPLC) but is also applicable to most other analytical instruments. This implementation would be very beneficial for the analysts/practitioners as the uncertainty would be handled within their everyday software environment.
Keywords: Measurement uncertainty estimation; ISO GUM; Analytical instruments; Instrument manufacturers; Software; HPLC
Ion chromatographic precision measurement procedure for electrolytes in human serum: validation with the aid of primary measurement procedures by Karin Röhker; Olaf Rienitz; Detlef Schiel (pp. 671-677).
In order to make analytical measurement results traceable to the SI units in the field of clinical chemistry, an ion chromatographic (IC) measurement procedure has been developed which allows the amount of substance of the four so-called electrolytes Na, K, Mg and Ca as well as that of Li to be determined efficiently in human serum and with high accuracy. The IC measurement procedure was validated using primary measurement procedures confirmed by international comparison measurements and is proposed for use as a transfer standard when comparing measurements with clinical reference laboratories. The solutions used for calibration were gravimetrically prepared from pure substances (salts). Their chemical compositions had been iteratively fitted to those of the samples. The serum samples were mineralized by microwave-assisted digestion. The following relative expanded uncertainties for the average elemental contents were obtained: Li 0.4%, Na 0.14%, K 0.6%, Mg 0.8% and Ca 0.4%.
Keywords: Ion chromatography; Traceability; Uncertainty budget; Clinical chemistry; Electrolytes
Achieving traceable chemical measurements: inter-laboratory evaluation of a simplified technique for isotope dilution mass spectrometry. Part 2. Methodology for high accuracy analysis of organic analytes by Mike Sargent; Gerry Newman; Ken Webb (pp. 678-683).
A high accuracy measurement procedure developed and validated at LGC has been transferred to a number of expert UK laboratories, and their experience in applying the technique has been evaluated by inter-laboratory comparisons. It is an “exact matching” calibration procedure for analysis of organic analytes using isotope dilution mass spectrometry (IDMS). This calibration procedure uses a calibration blend and a sample blend with closely matched isotope amount ratios, and is an iterative process, culminating in the calibration blend and sample blend having identical isotope amount ratios. It is capable of high accuracy, since systematic errors in the determination of the isotope amount ratios are cancelled out. A series of four inter-laboratory comparisons of increasing difficulty were carried out involving a number of expert laboratories. The first three comparisons used gas chromatography mass spectrometry (GC–MS) analysis of the pesticide metabolite (pp′-dichlorodiphenyl) dichloroethylene (pp′-DDE), involving both conventional calibration and IDMS exact matching procedures for pp′-DDE in a solvent and a complex liquid matrix (corn oil). The fourth comparisons utilised liquid chromatography mass spectrometry (LC–MS) and involved the analysis of sulphamethazine (4-amino-N-(4,6 dimethyl-2 pyrimidinyl) benzenesulphonamide) in solvent using IDMS and conventional calibration techniques. Following the first trial, a workshop for participants was held on the use of the exact matching procedure together with a short course on uncertainty estimation. The results of the comparisons clearly showed the superior accuracy of using IDMS with the exact matching procedure for both GC–MS and LC–MS applications. These comparisons and the workshop have enabled the methodology to be transferred to UK industry, helping to improve UK measurement capability.
Keywords: Isotope dilution; IDMS; Exact matching; Traceability
Regulatory aspects of proficiency testing: experience from the water sector by Michael Koch (pp. 684-687).
Proficiency tests in the regulated sector have requirements different from other areas. Repeated unsuccessful participation can lead to the economic ruin of a laboratory. This is illustrated at the water analyses sector in Germany as an example. Collusion and falsification have to be avoided. A special and uniform evaluation technique is necessary that includes the possibility of a common evaluation of different concentration levels and considers the skewed distribution of data. A suitable approach is published in a new German DIN standard (DIN 38402-45). The assessment of the values and the laboratories as a whole also needs special attention. A concept to do this with as few injustices as possible was developed in an inter-state working group in Germany.
Quality assurance and quality control in forest soil analyses: a comparison between European soil laboratories by Nathalie Cools; Véronique Delanote; Xavier Scheldeman; Paul Quataert; Bruno De Vos; Peter Roskams (pp. 688-694).
In transnational monitoring programmes, a balance between international reference methods, which improve spatial comparability, and national analysis methods that favour temporal comparability, by their use and testing over many years, needs to be sought. Prior to the next Pan-European Forest Soil Survey, a third interlaboratory comparison of soil analysis methods was organised. All participating laboratories were requested to use the same reference methods. Fifty-two soil laboratories from 27 European countries analysed a total of 48 soil parameters on three soil samples which were typical for European forest soils. The results of the statistical analysis showed a high interlaboratory and intralaboratory variability, especially for the acid oxalate extractions, particle size distribution, exchangeable elements and total carbonates. The intercomparability of the test results did not improve compared to the previous ring test. As the exercise aimed primarily at comparing the performance of the laboratories, it was not powerful enough to find cause–effect relationships between the meta information provided by the laboratories and the variability of the test results.
Keywords: Interlaboratory variability; Intralaboratory variability; Forest soil; Europe; Analytical quality control
Development of a novel approach for the production of dried genomic DNA for use as standards for qualitative PCR testing of food-borne pathogens by Stefanie Trapmann; Paolo Catalani; Jeffrey Hoorfar; Jozsef Prokisch; Pierre van Iwaarden; Heinz Schimmel (pp. 695-699).
As part of a multi-centre European project, FOOD-PCR, the feasibility of a novel approach for production of dried bacterial DNA that could be used as certified reference materials (CRM) was assessed. Selected strains of Salmonella typhimurium, Listeria monocytogenes, Escherichia coli O157, Campylobacter jejuni and Yersinia enterocolitica were used to produce genomic DNA (gDNA). These preparations gave support to method development for qualitative polymerase chain reaction (PCR) detection methods for food-borne pathogens. Purified gDNA was transformed into stable and dry gDNA by using polypropylene vials as carrier and applying a vacuum-drying technique. The gDNA preparations were shown to be sufficiently stable under ambient transport conditions without cooling and proved to have long-term stability at 5°C of at least 22 months. The dried DNA was easily reconstituted by addition of distilled water then gentle shaking. These studies have shown that production of stable and dry bacterial gDNA material is feasible and could help satisfy the increasing need for certified reference DNA positive control samples in the field of PCR testing for detection and verification of food-borne microbial pathogens.
Keywords: Genomic DNA; Standards; Certified reference material; Detection pathogenic bacteria; PCR
Imprecision and instability of common analytes in urine analysed by semi-automated dipstick urinalysis by Milan Skitek (pp. 700-703).
A diagnostic test can have a high diagnostic value if imprecision is low as possible. The imprecision of advanced automated dipstick urinalysis is well known; it is not well known in the many laboratories all over the world which still use semi-automated systems. After defining such imprecision we determined the instability of urinary specimens, which we retested after refrigeration for 24 h. The study was performed using the semi-automated Clinitek 500/Multistix 10 SG dipsticks (Bayer Corporation) system by comparing the imprecision (paired tests within 1 h) with repeated tests after 24 h (instability). The Clinitek 500/Multistix 10 SG has relatively low overall imprecision for blood/haemoglobin and protein, for which it meets high quality specifications, but not for leukocytes, for which minimum specifications are attained with a high false-negative rate (18.2%). The instability of all evaluated analytes is relatively low except for the leukocytes, for which minimum specification is not attained, with a false-negative rate of 30.3%, and partly attained for blood/haemoglobin, for which the minimum specification is attained with a false-negative rate of 11.3%. The imprecision remains a problem with semi-automated systems for urinalysis and is connected with the instability of urine specimens if analysis if delayed. After refrigeration for 24 h, there is a risk of false-negative results for leukocytes and blood/haemoglobin.
Keywords: Multiple test strip; Semi-automated dipstick urinalysis; Imprecision; Instability
SI-traceable certification of the IMEP-12 water sample combining contributions from different reference laboratories by I. Papadakis; R. Kessel; L. Van Nevel; J. Norgaard; Y. Aregbe; M. De Smet; P. Smeyers; Philip D. P. Taylor (pp. 704-710).
In the International Measurement Evaluation Programme (IMEP-12) comparison, a synthetically prepared water sample was offered to the analytical laboratories to perform measurements of As, B, Cd, Cr, Cu, Fe, Mg, Mn, Ni and Pb. The choice of elements to be measured was based on EU legislation, which the comparison was aiming to support. As to the IMEP policy, the laboratories’ results were presented according to the certified/assigned reference values established by several reference laboratories all around the world. The performed certification campaign is described in detail in this paper. Isotope dilution mass spectrometry (IDMS) was applied as a primary method of measurement (PMM), whenever possible, to achieve SI-traceable results. Apart from IDMS for reference measurements of some elements, k o-neutron activation analysis (k o-NAA) and external calibration (Ext-Calib) using inductively coupled plasma-mass spectrometry (ICP-MS) were applied. The reference values were characterised as “certified” (for B, Cd, Cr, Cu, Fe, Mg, Ni and Pb) or “assigned” (for As and Mn) according to the IMEP policy. Measurement uncertainty of the certified/assigned reference values was calculated according to the ISO/BIPM guide using the specialised software GUM Workbench.
Keywords: Water; Uncertainty; Traceability; Trace elements; Primary methods of measurement; Isotope dilution mass spectrometry; Certification campaign
The quality-management system in research implemented in the food and food process quality research laboratory of the French Food Safety Agency by Ronel Biré; Guy Tufféry; Hélène Lelièvre; Sylviane Dragacci (pp. 711-716).
The French Food Safety Agency is a public body incorporating 12 laboratories that perform research to support expertise and public decisions taken in the fields of sanitary safety of food, animal health, and veterinary drugs. On the request of the General Management of the Agency a quality-management system in research (QMSR) is being implemented in the Food and Food Process Quality Research Laboratory. The experimental QMSR is based on existing standards and documents, describing the provisions required for scientific and technical competence, quality management, and project management. Furthermore, this QMSR also incorporates specific notions of great importance for research activities such as the positive and negative non-conformities, the non-confirmation of hypotheses, and the principle of evaluation of a research activity by peers for both quality and scientific aspects.
Keywords: Quality assurance; Quality management in research; Food safety
Measurement uncertainty: practical problems encountered by accredited testing laboratories by Rob Visser (pp. 717-723).
Following the introduction of ISO 17025 in 1999, all accredited testing laboratories have started to implement a procedure for estimating measurement uncertainties for the analytical methods that they employ. These procedures and uncertainties are an integral part of the quality system of the accredited laboratory and are therefore reviewed during audits by the accreditation bodies. In January/February 2004 the status of measurement uncertainties available at accredited testing laboratories was evaluated. It was found that most laboratory customers do not make use nor want to make use of the available measurement uncertainties. Furthermore, the current lack of standardisation has caused the estimated measurement uncertainties to vary widely, even for the simplest determinations.
Keywords: Measurement uncertainty; Standardisation; Practical use; GUM; Accreditation; ISO 17025; Density; pH
About CCα and CCβ as introduced by the Commission Decision of 12 August 2002 implementing Council Directive 96/23/EC
by Elio Desimoni (pp. 724-725).
On the use of the correlation coefficient r for testing the linearity of calibration functions by Walter Huber (pp. 726-726).
This paper criticises the use of the correlation coefficient r for testing the linearity of calibration functions and recommends better methods.
Keywords: Test for linearity; Correlation coefficient rCoefficient of determination r2Calibration function
Policies, requirements and surveys concerning frequency for participation in proficiency testing schemes by Ulf Örnemark; Harald Fostel; Rolf Straub; Johannes van de Kreeke (pp. 729-732).
This paper focuses on policies and requirements concerning the frequency for participation in proficiency testing (PT) and provides an overview of the frequency for which PT activities are offered in 25 testing fields. Recent international surveys are summarised.
Keywords: Proficiency testing; External quality assessment; Frequency; Accreditation; Policy documents; Eptis