Proficiency assessment of laboratories undertaking hard coal analysis

The Institute for Chemical Processing of Coal in Zabrze, Poland, organized a proficiency testing round to determine the mass fraction of ash, total sulfur and total carbon and the value of gross calorific value. Forty-four participants from Polish heat and power plants, research entities and independent laboratories reported results. The performance of the participants was evaluated using z and E _n scores. Over 85 % of the participants reported satisfactory results indicating the high level of proficiency of the Polish laboratories in the field.     

Preparation of in-house reference material of benzylpenicillin in milk and results of a Brazilian proficiency testing scheme

Two milk test materials containing benzylpenicillin and a benzylpenicillin-free material were prepared and used for the operation of a Brazilian proficiency testing (PT) scheme according to the requirements of ISO/IEC 17043. The PT scheme was designed to include laboratories in charge of confirmatory analysis as well as screening analysis. Sets of sample vials, benzylpenicillin-free and spiked items containing 0.2 g of lyophilized milk, were distributed to each participant. Of 20 participants who reported screening data, 18 accomplished satisfying results, providing evidence of the capability of Brazilian laboratories to produce reliable qualitative information. The assigned value (robust average calculated from 6 results) and its uncertainty were (8.28 ± 0.52) μg/L. Participants’ performance was evaluated using z-scores. A small number of participants were able to report quantitative benzylpenicillin results, and consequently care should be taken in the interpretation of the laboratory’s performance, considering the statistical nature of z-scores. Long-term stability testing on remaining PT items showed that a stable benzylpenicillin quality control material was produced and can be used for internal quality control or validation purposes.     

External quality assessment in microbiology: comparison of results from Belgian and Canadian laboratories with regard to their ability to identify <Emphasis Type="Italic">Streptococcus pyogenes</Emphasis>

Clinical Microbiology Proficiency Testing (CMPT; Canada) and the Institute of Public Health (IPH; Belgium) set up a joint external quality assessment (EQA) project in which they sent identical simulated clinical samples to their respective participants. Samples were sent out as throat swabs containing Streptococcus pyogenes (as pathogen) and viridans streptococci (as commensal). Results from identification by the Belgian laboratories were excellent: 99.5% detected the group A streptococci. About 10% of the Canadian laboratories reported the absence of reportable β-haemolytic streptococci, although for most of them the issue was one of non-examination of small or pin-point streptococci. Overall, Canadian and Belgian laboratories performed well in this EQA; the joint project clearly showed that although many similarities exist, there are differences between laboratories in treating EQA samples and reporting results.     

Evaluation of the performance of 57 Japanese participating laboratories by two types of z-scores in proficiency test for the quantification of pesticide residues in brown rice

A proficiency test for the analysis of pesticide residues in brown rice was carried out to support upgrading in analytical skills of participant laboratories. Brown rice containing three target pesticides (etofenprox, fenitrothion, and isoprothiolane) was used as the test samples. The test samples were distributed to the 57 participants and analyzed by appropriate analytical methods chosen by each participant. It was shown that there was no significant difference among the reported values obtained by different types of analytical method. The analytical results obtained by National Metrology Institute of Japan (NMIJ) were 3 % to 10 % greater than those obtained by participants. The results reported by the participant were evaluated by using two types of z-scores, that is, one was the score based on the consensus values calculated from the analytical results of participants, and the other one was the score based on the reference values obtained by NMIJ with high reliability. Acceptable z-scores based on the consensus values and NMIJ reference values were achieved by 87 % to 89 % and 79 % to 94 % of the participants, respectively. Graphical Abstract

Distribution of z and z_NMIJ-scores for isoprothiolane     

Performance evaluation of polycyclic aromatic hydrocarbons analysis in sediment from proficiency testing with metrological reference values

This paper describes a metrological approach to evaluate the measurement capability of laboratories participating in two proficiency testing (PT) programmes involving the analysis of five polycyclic aromatic hydrocarbons (PAHs) in sediment samples. Reference values of PAHs in the programmes for performance assessment were obtained from an accurate isotope dilution gas chromatography mass spectrometry (ID-GCMS) method which was thoroughly validated and verified. Isotope dilution mass spectrometry (IDMS) technique usually has a well-defined measurement uncertainty budget and a traceability link to an International System of Units. Provision of the metrological reference values in PT enables the establishment of a technical platform to assess the actual competence of the participating laboratories in sediment PAHs analysis. Results of the PT programmes showed that about 80 % of the laboratories employed gas chromatography in their analyses and the remaining used liquid chromatography. Irrespective of the techniques being used, however, the majority of the participating laboratories were observed to underestimate values in which the mean values of the five reported PAHs were less than those of the ID-GCMS-derived reference values by 13–20 %. Only 41–44 % of the participating laboratories were able to achieve satisfactory z-scores. The present study revealed that the reinforcement of the capability for accurate measurement of PAHs in sediment samples in laboratories worldwide should be addressed.     

Analytical performance is improved by regular participation in proficiency testing: an analysis of data from the Aquacheck proficiency testing scheme

Analysis of historical data from the Aquacheck proficiency testing scheme demonstrates improvement in the performance of participants correlated to the frequency of participation. Analysis of the spread of results returned by all participants, defined by the percentage relative standard deviation (RSD) and the performance (Z) scores awarded to the individual participants, indicates that the overall performance for the group of participants is consistent. However, when the frequency of participation is analysed, it can be clearly seen that those laboratories who participated in the majority of the distributions available reported 10–15% more acceptable (Z-scores between +2 and ?2) results than those labs who took part with a greatly reduced frequency. When ‘more difficult’ analytes are considered, those laboratories who participated in greater than 75% of available rounds reported up to 30% more acceptable results than those laboratories who participated in 25% or fewer, of the available rounds.     

Evaluation of proficiency tests in microbiological analysis: enumeration of aerobic microorganisms

South Korea’s Ministry of Food and Drug Safety (MFDS) has been developing programs for the inspection and accreditation of food sanitation inspection institutions. Food sanitation inspection institutions such as MFDS regional offices, the Research Institute of Public Health and Environment and authorized private service providers in South Korea must participate in proficiency testing (PT) programs to comply with the Food Sanitation Act and MFDS Notification No. 2012-112. As the PT provider, the MFDS annually plans various microbiological and chemical PT programs for foods, cosmetics, and pharmaceutical products in accordance with ISO/IEC 17043. The aim of this project was to evaluate the performance of microbiological PT programs to ensure the quality of their routine test results. The test materials used were freeze-dried BioBalls from BTF Pty Ltd. Homogeneity and stability were investigated to assess the adequacy of the selected test materials. This project also contains data from inter-laboratory comparisons organized by MFDS in 2011 and 2012. More than 50 laboratories attended the PT program and submitted their results. Laboratory results were rated with z-scores according to the international standard ISO 13528. The results from 2011 and 2012 revealed that all participating laboratories had similar levels of proficiency. Most of the participants received a rating of “Satisfactory.” Moreover, the percentage of participants who received a rating of “Unsatisfactory” decreased from 3.5 % in 2011 to 2.0 % in 2012.     

Long-term external quality assessment program for CD4+ T-lymphocyte enumeration in Thailand

The accuracy and reliability of CD4+ T-lymphocyte enumeration are crucial for HIV healthcare management. Thailand’s CD4 external quality assessment (EQA) program was implemented in 2003. This program aims to improve the quality of CD4 testing by providing the quality control material, remedial action, and technical training. In this article, the overall longitudinal performance of the participating laboratories from 2003 to 2015 is reported. The EQA blood samples were sent to the participating laboratories in Thailand and other Southeast Asian (SEA) countries. The participants were requested to enumerate CD3+ and CD4+ T-lymphocytes. The trimmed mean, standard deviation (SD), coefficient of variation (CV), and standard deviation index (SDI) of both fraction and number were calculated from the returned data. Our result indicated a continuously increasing number of participants. The response rate of 72 trials was 98 %. The outlier rates for the fraction and number of CD4+ T-lymphocytes were 3.3 % and 3.4 %, respectively. The average CV of the fraction and number of CD4+ T-lymphocytes was 7.1 % and 9.4 %, respectively. In addition, the analysis of our current EQA trial no. 072 revealed that more than 98 % of participating laboratories had SDI values between ?2 and +2 for both fraction and number of CD3+ and CD4+ T-lymphocytes. In conclusion, the implementation of the CD4 EQA program in Thailand and other SEA countries has led to a reduction in the variability of the results of the CD4 count between laboratories and a continuous improvement in laboratory performance.     

Quality control in extended measurement campaigns: selection of contract laboratories by proficiency testing exemplified for the trace analysis of anilines in groundwater

An interlaboratory comparison for the determination of aniline, nine methylated anilines and chlorinated anilines in contaminated groundwater (each compound between 1 µg L^?1 and 750 µg L^?1) was conducted as proficiency test for the selection of contract laboratories for a groundwater monitoring campaign. For the 13 participants, two different test sample series were prepared from a stabilized real case groundwater. Series A was the groundwater as sampled in the field and series B was prepared from series A by spiking with selected anilines. Homogeneity and stability investigations revealed that contaminated groundwater provides a viable basis for the preparation of ring test samples for the determination of anilines. Analytical procedures were limited to the standardized liquid–liquid extraction or solid-phase extraction in combination with gas chromatography/mass spectrometry (DIN 38407-16:1999). The robust consensus values were evaluated according to the standardized protocol of DIN 38402-45:2013. Robust reproducibility standard deviations ranged largely between 20?% and 60?% depending on the analyte. The proficiency assessment of individual participants combined the qualitative aspect of correct peak identification with the quantitative determination of individual concentrations within set limits in a unified approach. It could be shown that the accreditation status of laboratory and the existence of a standardized analytical procedure do not substitute a problem-related proficiency assessment of potential contractors.     

Reproducibility of Mooney viscosity measurements made at different laboratories—A discussion of the problem

A cross-check with 12 participants has shown considerable differences between Mooney viscosity readings of different laboratories on four polymers. The mean difference for the identically prepared polymers was 7·7 MU (Mooney units) and the differences for individual polymers up to 11 MU. When the samples were prepared by the individual participants the differences were 7·4 MU for this viscosity range. The author attributes these differences partly to non-compliance with the standards as to the instruments and sample preparation and partly to vagueness of the standards themselves.Although definite amendments to the standards can be suggested, improvement of the instruments cannot be achieved at short notice. The differences between the measurements of different laboratories should therefore be ascertained through routine testing of standard samples; they could then be taken into account in the polymer delivery specifications.     

French laboratory proficiency testing program for food microbiology

The proficiency testing program in food microbiology (Réseau d'Analyses et d'Echanges en Microbiologie des Aliments; RAEMA), created in 1988, currently includes 440 participating laboratories. The program establishes proficiency in detection of Salmonella and Listeria monocytogenes, as well as quantitation of aerobic microorganisms, Enterobacteriaceae, coliforms, Escherichia coli, Clostridium perfringens, coagulase-positive Staphylococcus, and Listeria monocytogenes. Twice a year, 5 test samples are sent to participants to assess their precision and trueness for enumeration and detection of microorganisms. Results show an increasing involvement of food microbiology laboratories in quality assurance programs and use of standard and validated analytical methods. However, the percentage of laboratories obtaining questionable and unsatisfactory microbiological results remains relatively constant.     

Proficiency testing programmes as a tool in food quality assurance: Overview of Italian experiences

Proficiency testing involves the performance of test procedures on routine samples by a number of laboratories. Interlaboratory proficiency testings provide multiple benefits to participants since they play a key-role in the total quality control of laboratory activities. They serve as a means of self-improving, as a mechanism of continuing education and as a source of information for accreditation agencies. This review highlights basic principles, benefits, criteria and capabilities of a proficiency testing programme for food analysis laboratories as well as their role in the implementation of rapidly developing food control legislation.     

Lessons from the first international proficiency test for the detection of spores from the honey bee pathogen Paenibacillus larvae

We report on the first proficiency test in the context of honey bee disease testing on a broad international scale. Honey samples were distributed to 12 participating laboratories for isolation and identification of spores of the etiological agent of American foulbrood, Paenibacillus larvae. Of the 11 laboratories responding to this proficiency testing event, only 6 (54%) provided data that were in full agreement with the previously determined status of the honey samples; eight (72%) laboratories fell within the threshold for qualification as defined a priori in this proficiency test (=level of agreement of at least 90%). Some lessons can now be drawn from the organizational point of view and will certainly improve new initiatives to be taken.     

Proficiency testing in the light of a new rationale in metrology

The novel proposed definition of measurement result in the international metrology vocabulary requires a revision of standards and guidelines for proficiency testing (PT), and a new approach to processing proficiency data is needed to test the ability of laboratories to present not only unbiased quantity values, but reliable estimates of their uncertainty. Hence, an accepted reference value with the smallest possible uncertainty is needed to ascertain the proficiency of laboratories reporting results with lower than average uncertainty. A strategy based on the T-statistic is proposed leading to an accepted reference value that fully reflects the uncertainties reported by participants in a PT scheme and permits calculation of E _n numbers to distinguish whether or not measurement results are consistent with the accepted definition of the measurand. The strategy is applied to PT data from a recent international laboratory intercomparison of uranium isotopic ratios.     

Development of a proficiency testing scheme for a limited number of participants in the field of natural water analysis

A proficiency testing (PT) scheme was developed for a limited number of analytical laboratories participating in the analysis of natural water in Israel. Three fit-for-intended-use reference materials (RMs) were prepared for a pilot PT from natural water: RM-blank and two in-house reference materials (IHRMs) with seven analytes fortified to achieve different levels of analyte concentrations. The measurands for the PT participants were the traceable spike values certified in the IHRMs, i.e., added mass concentrations of the analytes. The RM-blank and IHRMs were found to be homogeneous and stable over 11 days, the time necessary for the experimental part of the PT. The RMs were distributed to the PT participants as unknown test items similar to routine samples. The test results were evaluated using their deviations from the IHRM-certified values. Eight Israeli laboratories took part in the interlaboratory comparison. Individual laboratory performance and metrological compatibility of the PT results of the participants, as a local group of laboratories, were evaluated for every analyte.     

Proficiency testing schemes for the assessment of Legionella PCR methodologies

Standard operating procedures used for the detection of bacteria in environmental samples are primarily based on bacterial growth on specific culture media and confirmation by biochemical and/or immunological tests. In the case of Legionella, isolation on BCYE-?? medium is the standard method, although it presents a number of drawbacks, and for this reason, the implementation of molecular methods, mainly those based on PCR, has increased over the last years. Following the ISO/IEC 17025, laboratories need an external evaluation of their work to assure the quality of the results they are producing, and the participation in proficiency testing (PT) schemes is compulsory. For those water-testing laboratories using PCR methods for Legionella, we have developed a PT scheme accredited according to ISO/IEC 17043. The preparation and the statistical analysis of the results are performed following this standard and the ISO 13528. The used samples have a very rapid and easy to use format, consisting of tablets with inactivated freeze-dried Legionella cells or freeze-dried Legionella DNA. In this PT scheme, participants evaluate both Legionella pneumophila and Legionella spp. detection systems and control the whole PCR process from the water sample concentration until the PCR results.     

Evaluation of bias,precision, and systematic errors in proficiency testing of Cl<Superscript>−</Superscript> and Cu concentration in water

The proficiency testing exercise was conducted to assess the quality of water testing in several laboratories in India. The 11 participants from all over India gathered at one place and attended the workshop organized at NEERI, Nagpur. The test samples were analyzed for Cl⁻ (Chloride) and Cu (Copper) concentration in water. The objective of the study was to determine bias and precision among participants for the analysis of Cl⁻ and Cu concentration. Statistical analysis indicated that most of the measurement results were overestimating the Cl⁻ concentration and underestimating the Cu concentration. The presence of systematic error identified the need for further improvement in determining the Cu concentration in water by the participants.     

The current status and future of medical laboratory quality regulation and accreditation in Ghana

High-quality and reliable laboratory services are important components of effective and well-functioning health systems. Accurate, reliable and timely medical laboratory testing is crucial to patient care and disease surveillance. Unfortunately, in many sub-Saharan African countries, medical laboratory systems are adversely affected by the unavailability of medical laboratories, poor laboratory infrastructure and lack of well-trained personnel [1]. Quality in the laboratory is only achieved in a systematic way through the implementation of a quality management system. The results of the study showed that approximately 60?% of the 78 respondents were unaware of the requirements of ISO 15189:2007. A trial of proficiency testing, termed ??blind proficiency testing??, was carried out in which 19 laboratories determined the concentrations of urea and cholesterol in a proficiency testing material. Of the 19 laboratories that determined the concentration of urea, 63?% produced satisfactory results with scores between ?2 and +2. Similarly, 63?% of the participating laboratories obtained satisfactory z scores for cholesterol determination. Some of the laboratories that obtained satisfactory scores for urea determination had unsatisfactory scores for cholesterol determination and vice versa. It is recommended that the Ghanaian government pass a law and establish a standard to regulate medical laboratories in Ghana in order to improve quality in a significant way.     

An interlaboratory study as useful tool for proficiency testing of chemical oxygen demand measurements using solid substrates and liquid samples with high suspended solid content

In 2008, the first Proficiency Testing Scheme of Chemical Oxygen Demand (1^stCOD-PT^ADG) was conducted to assess the results obtained for different research groups whose field work is mainly anaerobic digestion. This study was performed using four samples, two solid samples as raw materials and two solid samples to prepare high concentration suspended solid solutions. Invitations were sent to a large number of laboratories, mainly to anaerobic digestion research groups. Finally, thirty labs from sixteen countries agreed to participate, but for different reasons four participants could not send any data. In total, twenty-six results were reported to the COD-PT coordinator.This study showed the importance of continuous participation in proficiency testing (PT) schemes in order to compare the results obtained. Taking into account the lack of a general standard method and high quality certified reference materials (CRMs), the traceability of COD determination is not currently easy to check. In addition, the spread of participants’ results obtained was high and pointed to the advisability of using consensus values due to their unreliability. Therefore, the theoretical oxygen demand (ThOD) values were considered as assigned values for all the samples analysed. On the other hand, in this PT the established standard deviation (ESD) has been determined by the Horwitz modified function.Participants of this 1^stCOD-PT^ADG were asked to give a short report on the analytical method used. Although all the participants used potassium dichromate as their oxidant reagent, their experimental procedures were very different. With the purpose of comparing the results obtained, the different experimental conditions used were classified into five methods, corresponding to two main categories, open and closed reflux. The performance of laboratories was expressed by the z-score, whose value is considered satisfactory when z-score ≤±2. The overall analytical data evaluation showed that 64% of z-scores obtained were outside the accepted limits.