Proficiency testing in analytical chemistry, microbiology and laboratory medicine: working discussions on current practice and future directions

A summary of the working group (WG) discussions on proficiency testing (PT) and external quality assessment (EQA) held at the EURACHEM Workshop, Istanbul, 3?C6 October 2011, is provided. The six WGs covered a range of issues concerned with current practice and future directions; implementing the requirements of ISO/IEC 17043 by PT/EQA providers (WG1); accrediting PT/EQA providers to ISO/IEC 17043 (WG2); pre- and post-analytical aspects in PT/EQA (WG3); evaluating participant performance in qualitative PT/EQA schemes (WG4); establishing PT/EQA schemes in developing countries (WG5); and establishing acceptability criteria in microbiology PT/EQA schemes (WG6). Delegates with different backgrounds were on each WG in order to capture a range of views and experience from a number of different sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes and end-users of PT results such as accreditation bodies and regulatory authorities, from countries around the world.     

Proficiency testing in analytical chemistry, microbiology and laboratory medicine: working discussions on current practice and future directions

A summary of the working group (WG) discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Rome, 5–7 October 2008 is provided. The eight WG’s covered a range of issues concerned with current practice and future directions; how frequently should laboratories participate in PT/EQA? (WG1); developments in PT/EQA within the EU—what is required in future? (WG2); what issues do developing countries face with regards to PT/EQA? (WG3), what issues are specific to microbiology PT/EQA? (WG4); what new fields are emerging for PT/EQA? (WG5); what will be the impact of the new ISO/IEC 17043 standard? (WG6); do current PT/EQA schemes meet the needs of participants? (WG7); and what are the issues that affect the quality of proficiency test items? (WG8). Delegates with different backgrounds were on each WG in order to capture a range of views and experience from a number of different sectors. Working group representatives included PT/EQA providers, participants in PT/EQA schemes and end users of PT results such as accreditation bodies and regulatory authorities, from countries around the world.     

Proficiency testing in analytical chemistry, microbiology, and laboratory medicine – working group discussions on current status, problems, and future directions

Working group (WG) discussions on proficiency testing (PT) held at the joint Eurachem/ EQALM workshop, Borås, Sweden, 24–26 September 2000 are summarized. The discussions focused on aspects of PT and accreditation (WG 1), general aspects of PT in analytical chemistry (WG 2), microbiology (WG 3), and laboratory medicine (WG 4), incorporation of measurement uncertainty into PT schemes (WG 5), international harmonization of PT schemes (WG 6), and the role of PT in the international structure of chemical measurement (WG 7). Current status, problems and future directions are identified. Each WG contained a majority of participants experienced in the subject being covered by that WG, and a few participants with different expertise. This was done to promote cross-fertilization of ideas between sectors, a key objective of the workshop. The WG issues reflected the content of the keynote lectures and some issues were covered from different perspectives by more than one group.     

Proficiency testing in analytical chemistry,microbiology and laboratory medicine – working group discussions on current status,problems and future directions

Working group (WG) discussions on proficiency testing and external quality assessment held at the Eurachem workshop, Portorož, Slovenia 26–27 Sept 2005 are summarised. The discussions focused on performance criteria (WG 1), different aspects of accreditation (WGs 2–3), the revised international harmonised protocol (WG 4), pre- and post-analytical schemes (WG 5), Internet applications (WG 6), experience from the CoEPT project (WG 7), and future aspects (WG 8). Current status, problems and future directions were identified. The WG contained a mix of participants with different expertise. This was done to promote cross-fertilisation of ideas between sectors. The WG issues reflected the content of the keynote lectures and some issues were covered from different perspectives by more than one WG.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia.     

Surveys on the accreditation of providers of proficiency testing and external quality assessment schemes

Two surveys among providers of proficiency testing (PT) and external quality assessment (EQA) schemes were carried out during 2004 and 2005. The main objectives were to explore the current status of accreditation/certification and collect the providers’ views. Information based on the response from 160 providers in 32 countries reveals a strong tendency towards accreditation of PT/EQA. It is shown that this type of accreditation is based on several combinations of normative documents, hence illustrating a lack of harmonisation of national accreditation bodies. The surveys also show that schemes are operated under considerably different conditions and that providers’ competence may or may not be underpinned by other certification and/or accreditation. This paper elaborates on a number of issues related to PT/EQA accreditation, including customers’ views, normative documents, providers’ experience from the accreditation process, views expressed by international organisations, and effects of accreditation on participation fees, quality and availability.     

Addressing issues associated with the development and management of PT programs and with their optimum use

Over 200 participants from 54 countries took part in working group (WG) discussions on proficiency testing (PT) held in conjunction with the Global Odyssey 2002 conference on 24–26 February, 2002 in Atlanta, Georgia, USA. Each WG addressed a series of questions focusing on the role of PT in laboratory quality management (WG1), alternatives to traditional PT (WG2), international aspects of PT programs (WG3), quality management of PT programs (WG4), how to assess laboratory performance (WG5), and developing and funding PT for resource-limited countries and regions (WG6). Each large WG was further subdivided into smaller groups to allow maximum participation, which was one objective of the WGs. Some subgroups addressed the same questions, but in most cases they drew very similar conclusions. Individual participants were surprised to discover the truly global nature of some problems with PT, while at the same time how specific differences among countries or regions can either enhance or hinder opportunities to implement PT programs. Received: 13 April 2002 Accepted: 25 April 2002     

Proficiency testing in analytical chemistry,microbiology and laboratory medicine: discussions on current practice and future directions

Accreditation and Quality Assurance - A summary of the working group discussions on proficiency testing (PT) and external quality assessment (EQA) held at the Eurachem Workshop, Portorož,...     

Uses and abuses of PT

Proficiency testing (PT) is a very valuable quality tool for laboratories making all kinds of analytical measurements, in chemistry, microbiology and laboratory medicine. Compared with other quality tools, which are largely concerned with INPUTS (e.g. staff training, calibration, documentation), PT is concerned with OUTPUTS (i.e. the actual results produced by the laboratory). The quality of routine measurements and results, which would normally be reported to customers, both internal and external, should be demonstrated. This is a major reason for many laboratories participating in PT, even if they are not accredited, or use very few, if any, other quality tools. This is important, for it enables the laboratory manager to measure the efficacy of the overall quality system, and to determine if the inputs to this are appropriate. This should be done in a spirit of learning—it was discussed at the previous workshop whether PT schemes are teachers or policemen, and the consensus was that MOST are teachers (or at least try to be). Learning from mistakes, investigating problems, implementing corrective actions and then observing whether thisis successful in the next PT represents what many in our profession would regard as a proper and effective use of PT. Although this may be the intended primary use of PT by laboratories, we must not forget that PT has other valid uses. In particular, the use of PT to demonstrate competence to third parties—accreditation bodies, regulators, and customers—has become more important in the last few years. However, this development, however valuable, can lead to abuse of PT scheme data. This paper will highlight briefly some examples of both proper use and abuse of PT. These are taken from my experience with PT schemes over many years.     

Interlinkages and recognition of proficiency-testing schemes

 Because proficiency testing (PT) is increasingly used for the accreditation of testing laboratories and as a tool for backing up existing multilateral recognition arrangements between accreditation bodies, the question of performance and comparability of the proficiency-test providers arises. In this paper different approaches to assess the equivalence of European PT schemes and the competence of their providers are presented. As a first step a workshop is proposed to agree on a pilot study. The final aim is to create confidence in the existing PT schemes in Europe and to use them as common European tools.     

Do we need to accredit proficiency testing schemes?

 Proficiency testing (PT) is being increasingly used as an important quality assurance tool for laboratories. The subject of quality of the providers of PT schemes has been discussed increasingly in recent years. Some countries have implemented systems for the accreditation of PT schemes. This paper looks at the background to the accreditation of PT schemes, the likely mechanisms which could be employed for accreditation, and some of the practical aspects.     

Performance evaluation for proficiency testing with a limited number of participants

Proficiency testing (PT) is an essential tool for laboratories to assess their competency. Also, participation in PT has become one of the mandatory requirements for laboratory to seek accreditation according to ISO/IEC 17025. For this reason, the effectiveness of performance evaluation by PT scheme is of great concern for the participants and for accreditation bodies as well. In practice, owing to unavailability of other appropriate alternatives, PT scheme providers may have to choose using consensus values to evaluate the performance of participants. However, such consensus values approach was not recommended by relevant international guidelines for PT schemes with limited number of participants. With the use of Monte Carlo simulation technique, this study attempted to investigate the effectiveness of using consensus values for performance evaluation in PT schemes with limited number of participants. The simulation process was schemed according to the statistical model provided by ISO 5725-1 for laboratory measurement results, which covered components like method bias, laboratory bias, and measurement precision. The effectiveness of the consensus value approach was expressed as the percentage of participants in a simulation run could get the same evaluation result, either satisfactory or unsatisfactory, against the “true value.” The findings indicated that the number of participants, choice of consensus values, mass fraction of analyte, method bias, laboratory bias, and measurement repeatability of participating laboratories would all affect the effectiveness of the consensus value approach but at different extent. However, under certain circumstances, use of consensus value could still be considered as an acceptable approach for performance evaluation even the number of participants was limited. Some of the findings were further verified using real data from PT schemes where appropriate certified reference materials or reliable reference values were available.     

Accrediting PT/EQA providers to ISO/IEC 17043

After many years and having several different attempts for the accreditation of proficiency testing provider (PT provider), there is finally one stand-alone standard defining the requirements for the competence of PT providers and therefore an internationally harmonised basis for the accreditation of proficiency test providers. Since February 2010, the ISO/IEC 17043:2010 has replaced ISO/IEC Guide 43:1997 and ILAC G 13:2007. The philosophy of the standard about subcontracting work is different to this of the standards mostly used for accreditation like ISO/IEC 17025:2005 or ISO/IEC 17020:2004, etc. Besides the planning of the proficiency tests (PT), the performance evaluation and the authorisation of the PT reports the ISO/IEC 17043:2010 allows subcontracting for the rest of the work when providing PTs. This is a challenge for the assessors to judge about the competence of a PT provider. In numerous paragraphs, the standard sets very detailed requirements. Nevertheless, there is room for interpretation. For these cases, for example, contracts for subcontractors, procedure for the advisory board, minimum requirements for PT certificates, etc., some proposals are given to enable harmonised approach for the assessment of PT providers.     

Evaluating participant performance in qualitative PT/EQA schemes

A basic principle that needs to be satisfied before a proficiency testing (PT)/external quality assessment (EQA) scheme is first introduced is that measurement and assessment of performance is possible. For qualitative analyses, data can be presented as ??percentage correct??, and these data can be aggregated to show trends and to facilitate monitoring performance over time. Alternatively data can be analysed to identify significant patterns or changes in practice, or to compare different categories. However, the most useful tool is the application of a numerical score to the results. A number of different scoring strategies can be used, varying in complexity depending on the nature and significance of the type of results generated. Examples from selected microbiological EQA schemes are presented.     

Low-CD4+ T-lymphocyte blood samples for external quality assessment of CD4 testing in resource-poor settings

External quality assessment (EQA) of CD4 testing is important for clinically monitoring of patients with HIV/AIDS. EQA materials are limited to blood samples from normal blood donors with normal CD4+ T-lymphocyte levels. This study aimed to develop low-CD4+ T-lymphocyte blood samples for CD4 EQA. CD4+ T-lymphocyte-depleted blood samples were prepared using a magnetic bead separation technique. These CD4+ T-lymphocyte-depleted blood samples were mixed with undepleted whole blood samples to obtain low-CD4+ T-lymphocyte blood samples. The percentage and the number of CD4+ T-lymphocytes were determined using a flow cytometer. An evaluation study of this low-CD4+ T-lymphocyte blood sample was performed by sending to participating laboratories to investigate the potential use as CD4 EQA material. Our results showed that a magnetic separation technique could be used to prepare low-CD4+ T-lymphocyte blood samples. CD4+ T-lymphocytes in the low-CD4+ T-lymphocyte blood samples ranged from 15 % to 18 % and 160–300 cell/μl, respectively. In addition, CD4 testing of our low-CD4+ T-lymphocyte blood samples could be achieved following both the single- and the dual-platform flow cytometric approaches. A pilot EQA investigation revealed that the CV values of the number and percentage of CD4+ T-lymphocytes were 14 % and 10 %, respectively. Having the low-CD4+ T-lymphocyte blood samples in our CD4 EQA program should ensure reliability and credibility of CD4 testing in Thailand and other resource-poor countries.     

The influence of a quality system according to ISO/IEC 17025 on the performance of Brazilian laboratories in proficiency testing in the environmental area

This paper presents a performance analysis of laboratories in proficiency testing (PT) with the main objective of evaluating whether having accreditation to ISO/IEC 17025 or not having an implemented quality system has an influence on the performance of these laboratories. This research was conducted with data from an accredited PT scheme of physical–chemical water analyses. Nine metals were considered in the analysis, with a total of 896 results. The performance indicator was z-score. The proposed analysis was conducted through statistical methods of analysis of variance, Dunnett’s test, Chi-square and cross-tabulation. It was verified that there is a significant difference between the performance of accredited laboratories, recognised laboratories, and laboratories that do not have an implemented quality system. It was established that an accredited or recognised quality system has a positive influence on the laboratory performance, resulting in a lower z-score (in module) and in a larger percentage of satisfactory results.     

Compartmentalization in TEMPO‐Mediated Radical Polymerization in Dispersed Systems: Effects of Macroinitiator Concentration

The influence of the initial macroinitiator concentration ([PT]₀) on compartmentalization effects (segregation effects and confined space effects) in 2,2,6,6‐tetramethylpiperidinyl‐1‐oxy (TEMPO)‐mediated radical polymerization of styrene in a dispersed system at 125 °C has been investigated by simulations employing modified Smith‐Ewart equations. The modeling approach accounts for compartmentalization of both propagating radicals and nitroxide, as well as the generation of radicals by thermal initiation of styrene. The manifestation of compartmentalization effects occurs at significantly greater particle diameters (d) for low [PT]₀; at [PT]₀ = 0.002 M , the polymerization rate, control and livingness are affected by compartmentalization for d < 120 nm, whereas the system behaves as in the corresponding bulk system for d > 45 nm at [PT]₀ = 0.2 M . The results are discussed with regards to the specific effects of compartmentalization on deactivation and bimolecular termination.

     

Preparation and Characterization of a Sol-Gel Prepared Ferroelectric Sandwich Structure

A novel silicon-based PbTiO₃/Pb(Zr,Ti)O₃/PbTiO₃ (PT/PZT/PT) sandwich structure has been prepared using a sol-gel method. The annealing temperature is greatly reduced compared with those structures without PT layers. Capacitance-voltage (C-V), leakage current-voltage (I-V), polarization-field (P-E), dielectric-frequency response and polarization fatigue of the sandwich structure are examined. The relative dielectric constant, the coercive field and the remanent polarization of the PZT films are measured to be about 900, 18 kV/cm and 16 C/cm² respectively. The current density is less than 5 × 10^–9 A/cm² below 200 kV/cm. The dielectric constant of the structure remains constant at low frequency, and decreases to some degree at high frequency. The retained polarization does not change significantly after 8 × 10⁹ read/write cycles. The PZT films are proved to have very good dielectric and ferroelectric properties. The new PT/PZT/PT sandwich structure can be valuable for memory devices and other applications.     

Computational chemistry and molecular simulations of phosphoric acid

Quantum mechanics (QM) calculations, molecular dynamics (MD) simulations using the condensed‐phase optimized molecular potentials for atomistic simulation studies (COMPASS) force field, and the atom‐centered density matrix propagation (ADMP) approach have been used to investigate properties of phosphoric acid (PA). QM using B3LYP/6‐31++G(d,p) density functional theory were used to calculate gas‐phase proton affinities and interaction energies of PA and its derivatives. Detailed single coordinate driving, followed by quadratic synchronous transit optimization was used to determine energy barriers for different proton transfer (PT) pathways. Determined energy barrier heights in ascending order are (unit: kJ/mol): H₃O⁺→H₃PO₄ (0); H₄P₂O₇→H₃PO₄ (2.61); H₃PO₄→H₂PO (5.31); H₄PO→H₃PO₄ (～7.33); H₃PO₄→H₄P₂O₇/H₃PO₄→H₃PO₄ (15.99); H₄P₂O₇→H₂O (28.61); H₃PO₄→H₂O (47.14). The COMPASS force field was used to study condensed‐phase properties of PA. Good agreement between experimental data and MD results including density, radial distribution functions, and self‐diffusion coefficient at different temperatures provides validation of the COMPASS force field for PA. Finally, preliminary ADMP studies on a cluster of three PA molecules shows that the ADMP approach can reasonably describe the PT and self‐dissociation processes in PA. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011     

Experiences from the assessment of proficiency testing providers

Following a pilot project in 2001–2002, UKAS accredited nine PT providers. During the course of the pilot and at subsequent surveillance visits, UKAS has gained experience in assessing organisations against the criteria detailed within ISO/IEC Guide 43-1:1997 and ILAC G13:2000. This article explores some of the key aspects that arose during the pilot and how UKAS has accommodated the addition of the accreditation of PT providers in to its range of services.Presented at the Eurachem PT Workshop September 2005, Portorož, Slovenia     

Comparative analysis of the spectrophotometry based total phenolic acid estimation methods

This paper proposes a total phenolic acid estimation technique for samples with unknown phenolic acid composition and preliminary sample screening in resource-constrained settings. Phenolic acids constitute one of the important secondary metabolites for industry and researchers, but appropriate technique for its estimation by rural entrepreneurs is unclear. This study compared spectrophotometric Arnov test (AT) and potassium iodate test (PT) on the basis of seven parameters namely input requirements, process, limit of detection (LOD), limit of quantification (LOQ), linearity range, interferences and different phenolic compounds response. As per the results of the study PT is better than AT in input requirements, process, interference and different phenolic compounds response whereas AT is better than PT in LOD, LOQ and linearity range. Therefore, the study concluded that PT could be more suitable for rural entrepreneurs.