Korean Proficiency Tests for Pesticide Residues in Rice: Comparison of Various Proficiency Testing Evaluation Methods and Identification of Critical Factors for Multiresidue Analysis

Establishing pesticide safety management for agricultural products necessitates accurate pesticide analysis at analytical laboratories. Proficiency testing is regarded an effective method for quality control. Herein, proficiency tests were carried out for residual pesticide analysis in laboratories. All samples satisfied the homogeneity and stability criteria of the ISO 13528 standard. The obtained results were analyzed using the ISO 17043 z-score evaluation. Both individual pesticide and multiresidue proficiency evaluations were performed, and the proportion of z-scores within the ±2 range ("Satisfactory" rating) obtained for seven pesticides ranged 79-97%. Of the laboratories, 83% were classified as Category A using the category A/B method, and these also received AAA ratings in the triple-A evaluations. Furthermore, 66-74% of the laboratories were rated "Good" via five evaluation methods based on their z-scores. The sum of weighted z-scores and scaled sum of squared z-scores were considered as the most suitable evaluation techniques, as they compensated for the drawbacks of good results and corrected the poor results. To identify the main factors affecting laboratory analysis, the experience of the analyst, sample weight, calibration curve preparation method, and cleanup status were considered. A dispersive solid phase extraction cleanup significantly improved the results (p < 0.01).

Statistical Analysis of the Performance of Local Veterinary Laboratories in Molecular Detection (rRT-PCR) of Avian Influenza Virus via National Proficiency Testing Performed during 2020-2022

For the early detection of avian influenza virus (AIV), molecular diagnostic methods such as real-time RT-PCR (rRT-PCR) are the first choice in terms of accuracy and speed in many countries. A laboratory's capability to perform this diagnostic method needs to be measured through external and independent assessment to ensure that the method is validated within the laboratory and in interlaboratory comparison. The Animal and Plant Quarantine Agency of Korea has implemented five rounds of proficiency testing (PT) for rRT-PCR targeting local veterinary service laboratories involved in the AIV national surveillance program from 2020 to 2022. In each round, a portion composed of six or more samples was selected from the entire PT panel consisting of H5, H7, and H9 viruses isolated in Korea and distributed to each participant, and at least one pair of samples was commonly included in each panel for interlaboratory comparison. During the five rounds of PT, a few incorrect and outlying results were detected that required immediate inspection or corrective actions. However, in the quantitative measurement of Ct values, the average standard deviation or coefficient of variation decreased as multiple PT rounds progressed, and a positive correlation between consecutive rounds of PT was observed since 2021. The better consistency or stability in the experimental performance appeared to contribute to the more harmonized results in the latest PTs, and it is assumed that the positive reaction of participants to the challenges of quantitative assessment reports showing their status intuitively might work. We need to continue operating the PT program for local laboratories because they play crucial roles at the front line of the national avian influenza surveillance program, and frequent changes in the human resources or environment for diagnosis in those laboratories are inevitable.

Intercomparison of Radon Flux Monitors at Low and at High Radium Content Areas under Field Conditions

Interlaboratory exercises are a good tool to compare the response of different systems to the same quantity and to identify possible inconsistencies between them. One of the main goals of the EMPIR 19ENV01 traceRadon project is to harmonize radon flux measurements based on different systems and methodologies. In the framework of the traceRadon Project, two radon flux intercomparison campaigns were carried out in October 2021 at high and at low radon source areas. Four institutions participated in the field intercomparison exercises with their own systems. Every system was based on a specific radon monitor (diffusion or pump mode) and an accumulation chamber (with manual or automatic opening). Radon fluxes were calculated by each participant using both exponential and linear fittings of the radon activity concentration measured over time within the accumulation chambers. The results of this study show mainly: (i) the exponential approach is not advisable due to the variability of the radon flux and the leakage of the systems during long-time measurements; (ii) the linear approach should be applied to minimize the measurement period in agreement with the time response and sensitivity of the monitors; (iii) radon flux measured at high radon source areas (radium content of about 800 Bq kg^-1) risks being underestimated because of the influence of advective effects; (iv) radon flux measured at low radon source areas (radium content of about 30 Bq kg^-1) may present large uncertainties if sensitive radon monitors with pump mode are not used.

Nurses' experiences of a recertification process involving a series of examinations to obtain a nursing license in a new country

AIM

To examine internationally educated nurses' (IENs') experiences of the recertification process when undergoing a series of examinations to test their nursing knowledge and skills and, thereby, obtain a Swedish nursing license.

DESIGN

A qualitative study with a descriptive design.

METHODS

A convenience sample of 15 IENs at the end of the recertification process was included. Data were collected using semi-structured telephone interviews between September 2019 and January 2021 and analysed using qualitative content analysis.

RESULTS

Conducting the recertification process to obtain a Swedish nursing license was challenging in many ways, and the nurses described a rollercoaster of emotions during the process: frustration, loneliness, stress and anxiety, but also happiness, pride and relief. The process was, for some, so demanding they almost gave up, and support was, therefore crucial for the nurses. However, many times, they had to struggle to find out where they could turn for help or guidance.

CONCLUSION

The nurses found the formal support during the recertification process to be inadequate and inaccessible. For this reason, and to decrease the risk of nurses dropping out and instead taking unlicensed jobs, there is a need to develop and introduce more supportive structures and to make the existing support and information more accessible for the nurses.

IMPACT

This study highlights the importance of offering accessible support during a demanding and challenging recertification process. These findings can help policymakers develop and introduce supportive structures in the process of recertification for IENs.

Interlaboratory Comparison Study on Ribodepleted Total RNA High-Throughput Sequencing for Plant Virus Diagnostics and Bioinformatic Competence

High-throughput sequencing (HTS) technologies and bioinformatic analyses are of growing interest to be used as a routine diagnostic tool in the field of plant viruses. The reliability of HTS workflows from sample preparation to data analysis and results interpretation for plant virus detection and identification must be evaluated (verified and validated) to approve this tool for diagnostics. Many different extraction methods, library preparation protocols, and sequence and bioinformatic pipelines are available for virus sequence detection. To assess the performance of plant virology diagnostic laboratories in using the HTS of ribosomal RNA depleted total RNA (ribodepleted totRNA) as a diagnostic tool, we carried out an interlaboratory comparison study in which eight participants were required to use the same samples, (RNA) extraction kit, ribosomal RNA depletion kit, and commercial sequencing provider, but also their own bioinformatics pipeline, for analysis. The accuracy of virus detection ranged from 65% to 100%. The false-positive detection rate was very low and was related to the misinterpretation of results as well as to possible cross-contaminations in the lab or sequencing provider. The bioinformatic pipeline used by each laboratory influenced the correct detection of the viruses of this study. The main difficulty was the detection of a novel virus as its sequence was not available in a publicly accessible database at the time. The raw data were reanalysed using Virtool to assess its ability for virus detection. All virus sequences were detected using Virtool in the different pools. This study revealed that the ribodepletion target enrichment for sample preparation is a reliable approach for the detection of plant viruses with different genomes. A significant level of virology expertise is needed to correctly interpret the results. It is also important to improve and complete the reference data.

Internationally harmonized certified reference materials and proficiency testings for pesticide residue analysis

Matrix certified reference materials (CRMs) and proficiency testings (PTs) are effective for evaluation of the quality of analytical results. The National Metrology Institute of Japan has developed five kinds of CRMs and has provided eight PTs so far for the quantification of pesticide residues in foods. Target pesticides were sprayed on growing crops, and the harvests were used for the preparation of CRMs and PT samples. In most cases, multiple analytical methods based on isotope dilution mass spectrometry were used to ensure the reliability of certified values (for CRMs) and reference values (for PT samples). These activities were carried out with corresponding to the international standards such as ISO 17034 and ISO/IEC 17043. An overview of the development of CRMs and the implementation of PTs is described, with some examples.

[Application, development, and challenges of capillary electrophoresis in disease prevention and control]

Since the advent of commercial instruments in 1989, capillary electrophoresis (CE) has advanced considerably, with improvement in reproducibility and accuracy in many application fields. CE is predominantly used in research on disease prevention and control, and hygienic chemical inspection. The applications of CE range from assessment of inorganic anions and cations in drinking water to that of biological macromolecules, such as nucleic acids, in pathogenic microorganisms. Since the analytical capacity of CE ranges from inorganic ions to cell, it has become an indispensable technique in this field, particularly in public health emergency and epidemic management. Universal non-targeted analyses to detect possible pathogens, and the capability of rapid and accurate testing of large numbers of specimens are required. In the analyses of polymerase chain reaction (PCR) products, nucleic acid sequencing, mutation detection and genotyping, food-borne disease pathogens, and vaccine analyses, CE methods characterized by high through-put and sensitivity are necessary. In the public health sector, CE is essential in the analyses of food (including emergency analyses for food poisoning), cosmetics, and disinfectants. Satisfactory results of the FAPAS (Food Analysis Performance Assessment Scheme) and domestic proficiency tests indicated the accuracy of CE in quantitative analyses. Application of CE in disease prevention and control is challenged by a number of new molecular biological methods, as optimizing CE methods may not be feasible, and results are difficult to interpret. CE methods, including transformation of peaks to identification of pathogens, can be an arduous task. Thus, end-users prefer using commercialized CE systems and reagents in their routine work. Alternatively, CE methods for analysis of small molecules in product analyses, such as food safety, cosmetics and disinfectant testing, is commonly performed. A plethora of studies published within the decade, indicate that CE is still an active research area in hygienic chemical inspection. To a large extent, CE has not been used for routine analysis in the centers for disease control and prevention, accredited laboratories in China, nor regulatory agencies worldwide. This may be due to the lack of practical protocols for the standards, and the misconceptions regarding the ease of use of CE, which could have hindered its widespread application. Although CE is an environmental friendly technique with minimal usage of toxic chemicals, few standard methods of CE exist in agriculture, environmental protection, food, beverage, chemical, and pharmaceutical industries in the United States, Britain, Europe, Japan, India, Brazil, Russia, and China. Since 2002, CE was used in our laboratory to analyze a large variety of samples. We found that once the CE method has been fully verified and described in detail, it was easily standardized. It is not necessary to screen the equivalent chromatographic column, or to use a specific liquid chromatographic (LC) column. This can effectively circumvent the challenge of shifting peak orders caused by different LC column selectivity. Once combined with general, high sensitivity detectors, CE can be used in the detection of bacteria or viruses in food safety, and play a greater role in the field of disease prevention and control. In the present review, applications of CE in nucleic acid detection for viruses and bacteria, analysis of vaccines, routine testing on food, dietary supplements, medical foods, cosmetics and disinfectants, proficiency tests, and emergency analyses of food poisoning were summarized. The applications and challenges of CE in the field of disease control and prevention were analyzed, and development of this technique was prospected.

[Evaluation of proficiency test with low number of participants:a case study on the testing of lead and nitrite in water]

OBJECTIVE

The gross error of the assigned value-classical statistical method was developed that all participants in proficiency testing activities could obtain unbiased evaluation in case of a low number of participants(& lt; 17).

METHODS

This developed method was employed to evaluate the testing result of nitrite-N and lead in water from participants along the "Belt and Road", which was organized by CNCA in 2019.

RESULTS

Use the specified value gross error-classical statistical method to evaluate the feedback result of 29(15+14) participants with non-normal distribution, 4 out of 15 participants in "Lead in Water" get a "unsatisfied", 5 out of the 14 participants in "Nitrite in Water(as Nitrogen)"get a "unsatisfactory".

CONCLUSION

When the robust statistics and classical statistical method are unable to make objective evaluations respectively, this method could mildly remove outliers and avoid the extreme evaluation of "all satisfied"or "all dissatisfied", which truly reflected the real ability of each participant and could be applied to the proficiency testing activity with low number of participants.

Metagenomics-Based Proficiency Test of Smoked Salmon Spiked with a Mock Community

An inter-laboratory proficiency test was organized to assess the ability of participants to perform shotgun metagenomic sequencing of cold smoked salmon, experimentally spiked with a mock community composed of six bacteria, one parasite, one yeast, one DNA, and two RNA viruses. Each participant applied its in-house wet-lab workflow(s) to obtain the metagenomic dataset(s), which were then collected and analyzed using MG-RAST. A total of 27 datasets were analyzed. Sample pre-processing, DNA extraction protocol, library preparation kit, and sequencing platform, influenced the abundance of specific microorganisms of the mock community. Our results highlight that despite differences in wet-lab protocols, the reads corresponding to the mock community members spiked in the cold smoked salmon, were both detected and quantified in terms of relative abundance, in the metagenomic datasets, proving the suitability of shotgun metagenomic sequencing as a genomic tool to detect microorganisms belonging to different domains in the same food matrix. The implementation of standardized wet-lab protocols would highly facilitate the comparability of shotgun metagenomic sequencing dataset across laboratories and sectors. Moreover, there is a need for clearly defining a sequencing reads threshold, to consider pathogens as detected or undetected in a food sample.

Proficiency Testing of Metagenomics-Based Detection of Food-Borne Pathogens Using a Complex Artificial Sequencing Dataset

Metagenomics-based high-throughput sequencing (HTS) enables comprehensive detection of all species comprised in a sample with a single assay and is becoming a standard method for outbreak investigation. However, unlike real-time PCR or serological assays, HTS datasets generated for pathogen detection do not easily provide yes/no answers. Rather, results of the taxonomic read assignment need to be assessed by trained personnel to gain information thereof. Proficiency tests are important instruments of validation, harmonization, and standardization. Within the European Union funded project COMPARE [COllaborative Management Platform for detection and Analyses of (Re-) emerging and foodborne outbreaks in Europe], we conducted a proficiency test to scrutinize the ability to assess diagnostic metagenomics data. An artificial dataset resembling shotgun sequencing of RNA from a sample of contaminated trout was provided to 12 participants with the request to provide a table with per-read taxonomic assignments at species level and a report with a summary and assessment of their findings, considering different categories like pathogen, background, or contaminations. Analysis of the read assignment tables showed that the software used reliably classified the reads taxonomically overall. However, usage of incomplete reference databases or inappropriate data pre-processing caused difficulties. From the combination of the participants' reports with their read assignments, we conclude that, although most species were detected, a number of important taxa were not or not correctly categorized. This implies that knowledge of and awareness for potentially dangerous species and contaminations need to be improved, hence, capacity building for the interpretation of diagnostic metagenomics datasets is necessary.

Fingerprint error rate on close non-matches

The accuracy of fingerprint identifications is critically important to the administration of criminal justice. Accuracy is challenging when two prints from different sources have many common features and few dissimilar features. Such print pairs, known as close non-matches (CNMs), are increasingly likely to arise as ever-growing databases are searched with greater frequency. In this study, 125 fingerprint agencies completed a mandatory proficiency test that included two pairs of CNMs. The false-positive error rates on the two CNMs were 15.9% (17 out of 107, 95% C.I.: 9.5%, 24.2%) and 28.1% (27 out of 96, 95% C.I.: 19.4%, 38.2%), respectively. These CNM error rates are (a) inconsistent with the popular notion that fingerprint evidence is nearly infallible, and (b) larger than error rates reported in leading fingerprint studies. We conclude that, when the risk of CNMs is high, the probative value of a reported fingerprint identification may be severely diminished due to an elevated false-positive error risk. We call for additional CNM research, including a replication and expansion of the present study using a representative selection of CNMs from database searches.

Intercomparison of Indoor Radon Measurements Under Field Conditions In the Framework of MetroRADON European Project

Interlaboratory comparisons are a basic part of the regular quality controls of laboratories to warranty the adequate performance of test and measurements. The exercise presented in this article is the comparison of indoor radon gas measurements under field conditions performed with passive detectors and active monitors carried out in the Laboratory of Natural Radiation (LNR). The aim is to provide a direct comparison between different methodologies and to identify physical reasons for possible inconsistencies, particularly related to sampling and measurement techniques. The variation of radon concentration during the comparison showed a big range of values, with levels from approximately 0.5 to 30 kBq/m³. The reference values for the two exposure periods have been derived from a weighted average of participants’ results applying an iterative algorithm. The indexes used to analyze the participants’ results were the relative percentage difference D(%), the Zeta score (ζ), and the z-score (z). Over 80% of the results for radon in air exposure are within the interval defined by the reference value and 20% and 10% for the first and the second exposure, respectively. Most deviations were detected with the overestimating of the exposure using passive detectors due to the related degassing time of detector holder materials.

Statistical Evaluation of Barkhausen Noise Testing (BNT) for Ground Samples

Barkhausen noise testing (BNT) is a nondestructive method for investigating many properties of ferromagnetic materials. The most common application is the monitoring of grinding burns caused by introducing locally high temperatures while grinding. Other features, such as microstructure, residual stress changes, hardening depth, and so forth, can be monitored as well. Nevertheless, because BNT is a method based on a complex magnetoelectric phenomenon, it is not yet standardized. Therefore, there is a need to study the traceability and stability of the measurement method. This study aimed to carry out a statistical analysis of ferromagnetic samples after grinding processes by the use of BNT. The first part of the experiment was to grind samples in different facilities (Sweden and Finland) with similar grinding parameters, different grinding wheels, and different hardness values. The second part was to evaluate measured BNT parameters to determine significant factors affecting BNT signal value. The measurement data from the samples were divided into two different batches according to where they were manufactured. Both grinding batches contained measurement data from three different participants. The main feature for calculation was the root-mean-square (RMS) value. The first processing step was to normalize the RMS values for all the measurements. A standard analysis of variance (ANOVA) was applied for the normalized dataset. The ANOVA showed that the grinding parameters had a significant impact on the BNT signal value, while the other investigated factors (e.g., participant) were negligible. The reasons for this are discussed at the end of the paper.

[Evaluation based on the results of international proficiency tests for aflatoxins and analysis of keypoint detection]

OBJECTIVE

To analyze the results of international proficiency tests for aflatoxin determination and to identify the requirement of quality assurance and control in mycotoxin analysis.

METHODS

By the use of Z-scores, the results of aflatoxins from international proficiency tests were analyzed and the critical control points in experimental operation were discussed.

RESULTS

The absolute values of the Z-scores of aflatoxins were less than 2, indicating that the results from the laboratory were satisfactory. The sampling and testing method had very important effects on the detection results.

CONCLUSION

The results of the international proficiency tests of aflatoxins suggested that to strengthen the critical control points in the experimental operation can effectively improve the accuracy and reliability of the determination results.

Proficiency testing by the National Metrology Institute of Japan for quantification of pesticide residues in grain samples from 2012 to 2018

From 2012 to 2018, proficiency testings (PTs) were carried out to support the analytical skill development of participants. Grains were sprayed with various target pesticides and used as material samples for PTs. It was found that 27-56% and 10-43% of participants used the Japanese official multiresidue method and a solid-phase extraction technique with the Quick, Easy, Cheap, Effective, Rugged, and Safe (modified QuEChERS, known as "STQ" in Japan) method, respectively. Reported results were evaluated using two types of z-scores: one was based on consensus values calculated from the analytical results reported by the participants, and the other was based on values obtained by the National Metrology Institute of Japan (NMIJ). Acceptable z-scores based on the consensus values and NMIJ reference values were achieved by 78-95% and 67-94% of the participants, respectively. Many laboratories improved their z-scores by continuing participation in our PT.

Proficiency of WHO Global Foodborne Infections Network External Quality Assurance System Participants in Identification and Susceptibility Testing of Thermotolerant Campylobacter spp. from 2003 to 2012

Campylobacter spp. are foodborne and waterborne pathogens. While rather accurate estimates for these pathogens are available in industrialized countries, a lack of diagnostic capacity in developing countries limits accurate assessments of prevalence in many regions. Proficiency in the identification and susceptibility testing of these organisms is critical for surveillance and control efforts. The aim of the study was to assess performance for identification and susceptibility testing of thermotolerant Campylobacter spp. among laboratories participating in the World Health Organization (WHO) Global Foodborne Infections Network (GFN) External Quality Assurance System (EQAS) over a 9-year period. Participants (primarily national-level laboratories) were encouraged to self-evaluate their performance as part of continuous quality improvement. The ability to correctly identify Campylobacter spp. varied by year and ranged from 61.9% (2008) to 90.7% (2012), and the ability to correctly perform antimicrobial susceptibility testing (AST) for Campylobacter spp. appeared to steadily increase from 91.4% to 93.6% in the test period (2009 to 2012). The poorest performance (60.0% correct identification and 86.8% correct AST results) was observed in African laboratories. Overall, approximately 10% of laboratories reported either an incorrect identification or antibiogram. As most participants were supranational reference laboratories, these data raise significant concerns regarding capacity and proficiency at the local clinical level. Addressing these diagnostic challenges is critical for both patient-level management and broader surveillance and control efforts.

GenomeTrakr proficiency testing for foodborne pathogen surveillance: an exercise from 2015

Pathogen monitoring is becoming more precise as sequencing technologies become more affordable and accessible worldwide. This transition is especially apparent in the field of food safety, which has demonstrated how whole-genome sequencing (WGS) can be used on a global scale to protect public health. GenomeTrakr coordinates the WGS performed by public-health agencies and other partners by providing a public database with real-time cluster analysis for foodborne pathogen surveillance. Because WGS is being used to support enforcement decisions, it is essential to have confidence in the quality of the data being used and the downstream data analyses that guide these decisions. Routine proficiency tests, such as the one described here, have an important role in ensuring the validity of both data and procedures. In 2015, the GenomeTrakr proficiency test distributed eight isolates of common foodborne pathogens to participating laboratories, who were required to follow a specific protocol for performing WGS. Resulting sequence data were evaluated for several metrics, including proper labelling, sequence quality and new single nucleotide polymorphisms (SNPs). Illumina MiSeq sequence data collected for the same set of strains across 21 different laboratories exhibited high reproducibility, while revealing a narrow range of technical and biological variance. The numbers of SNPs reported for sequencing runs of the same isolates across multiple laboratories support the robustness of our cluster analysis pipeline in that each individual isolate cultured and resequenced multiple times in multiple places are all easily identifiable as originating from the same source.

Preparation of Artificial Blood from the Extract of Legume Root Nodules, and the Creation of Artificial Latent Fingermarks in Blood Using Artificial Blood. J Forensic Sci 2017;63:234-238. [PMID: 28271501 DOI: 10.1111/1556-4029.13488]

Distribution of homogeneous fingermarks in blood is essential for conducting proficiency tests in forensic science. Hence, the artificial blood was prepared using the root nodule extract of Glycine max plants. The reactivity of the artificial blood with widely used human blood detection reagents was tested. Artificial latent fingermarks in blood were printed using an inkjet cartridge case filled with artificial blood solution. The artificial latent fingermarks in blood were developed with amino acid-sensitive reagents and could obtain development as prominent as the image of the master fingermark saved on the computer. Therefore, it has been confirmed that the extract of legume root nodules can be used as artificial blood, and the artificial blood can be used for the preparation of artificial latent fingermarks or footmarks in blood.

Proficiency Testing of Feed Constituents: A Comparative Evaluation of European and Developing Country Laboratories and Its Implications for Animal Production

Proficiency tests, with two feed samples each year, for various constituents (proximate, macro- and microminerals, feed additives, and amino acids) were conducted in 2014 and 2015. A total of 40 and 50 European and 73 and 63 developing country feed analysis laboratories participated in the study in 2014 and 2015, respectively. The data obtained from these two sets of laboratories in each year enabled a comparison of the performance of the European and developing country laboratories. Higher standard deviation and several-fold higher coefficients of variation were obtained for the developing country laboratories. The coefficients of variation for chemical composition parameters, macrominerals, microminerals, and amino acids were higher by up to 9-fold, 14-fold, 10-fold, and 14-fold, respectively, for the developing country laboratories compared with the European laboratories in 2014, while the corresponding values for 2015 were 4.6-fold, 4.4-fold, 9-fold, and 14-fold higher for developing county laboratories. Also, higher numbers of outliers were observed for developing countries (2014, 7.6-8.7% vs 2.9-3.0%; 2015, 7.7-9.5% vs 4.2-7.0%). The results suggest higher need for developing country feed analysis laboratories to improve the quality of data being generated. The likely impact of higher variability of the data generated in developing countries toward safe and quality preparation of animal diets, their impact on animal productivity, and possible ways to improve the quality of data from developing countries are discussed.

Organization and ELISA-Based Results of the First Proficiency Testing to Evaluate the Ability of European Union Laboratories to Detect Staphylococcal Enterotoxin Type B (SEB) in Buffer and Milk

The aim of this work was to organize the first proficiency test (PT) dedicated to staphylococcal enterotoxin B (SEB) detection in milk and buffer solutions. This paper describes the organization of the PT trial according to EN ISO 17043 requirements. Characterization of the SEB stock solution was performed using SDS-PAGE and SE-specific ELISA, and amino acid analysis was used to assign its protein concentration. The solution was then used to prepare six PT materials (four milk and two buffer batches) at a ng/g toxin level, which included one blank and one SEA-containing milk as specificity control. Suitable material homogeneity and stability were assessed using screening and quantitative ELISAs. Among the methods used by the participants, ELISA-based methods demonstrated their efficiency for the detection of SEB in both simple and complex matrices. The results serve as a basis for further improving the detection capabilities in expert laboratories and can therefore be considered as a contribution to biopreparedness.

An International Proficiency Test to Detect, Identify and Quantify Ricin in Complex Matrices

While natural intoxications with seeds of Ricinus communis (R. communis) have long been known, the toxic protein ricin contained in the seeds is of major concern since it attracts attention of those intending criminal, terroristic and military misuse. In order to harmonize detection capabilities in expert laboratories, an international proficiency test was organized that aimed at identifying good analytical practices (qualitative measurements) and determining a consensus concentration on a highly pure ricin reference material (quantitative measurements). Sample materials included highly pure ricin as well as the related R. communis agglutinin (RCA120) spiked into buffer, milk and meat extract; additionally, an organic fertilizer naturally contaminated with R. communis shred was investigated in the proficiency test. The qualitative results showed that either a suitable combination of immunological, mass spectrometry (MS)-based and functional approaches or sophisticated MS-based approaches alone successfully allowed the detection and identification of ricin in all samples. In terms of quantification, it was possible to determine a consensus concentration of the highly pure ricin reference material. The results provide a basis for further steps in quality assurance and improve biopreparedness in expert laboratories worldwide.

Recommended Immunological Assays to Screen for Ricin-Containing Samples

Ricin, a toxin from the plant Ricinus communis, is one of the most toxic biological agents known. Due to its availability, toxicity, ease of production and absence of curative treatments, ricin has been classified by the Centers for Disease Control and Prevention (CDC) as category B biological weapon and it is scheduled as a List 1 compound in the Chemical Weapons Convention. An international proficiency test (PT) was conducted to evaluate detection and quantification capabilities of 17 expert laboratories. In this exercise one goal was to analyse the laboratories’ capacity to detect and differentiate ricin and the less toxic, but highly homologuous protein R. communis agglutinin (RCA120). Six analytical strategies are presented in this paper based on immunological assays (four immunoenzymatic assays and two immunochromatographic tests). Using these immunological methods “dangerous” samples containing ricin and/or RCA120 were successfully identified. Based on different antibodies used the detection and quantification of ricin and RCA120 was successful. The ricin PT highlighted the performance of different immunological approaches that are exemplarily recommended for highly sensitive and precise quantification of ricin.

Characterization of Ricin and R. communis Agglutinin Reference Materials

Ricinus communis intoxications have been known for centuries and were attributed to the toxic protein ricin. Due to its toxicity, availability, ease of preparation, and the lack of medical countermeasures, ricin attracted interest as a potential biological warfare agent. While different technologies for ricin analysis have been established, hardly any universally agreed-upon "gold standards" are available. Expert laboratories currently use differently purified in-house materials, making any comparison of accuracy and sensitivity of different methods nearly impossible. Technically challenging is the discrimination of ricin from R. communis agglutinin (RCA120), a less toxic but highly homologous protein also contained in R. communis. Here, we established both highly pure ricin and RCA120 reference materials which were extensively characterized by gel electrophoresis, liquid chromatography-electrospray ionization-tandem mass spectrometry (LC-ESI MS/MS), and matrix-assisted laser desorption ionization-time of flight approaches as well as immunological and functional techniques. Purity reached >97% for ricin and >99% for RCA120. Different isoforms of ricin and RCA120 were identified unambiguously and distinguished by LC-ESI MS/MS. In terms of function, a real-time cytotoxicity assay showed that ricin is approximately 300-fold more toxic than RCA120. The highly pure ricin and RCA120 reference materials were used to conduct an international proficiency test.

Qualitative and Quantitative Detection of Botulinum Neurotoxins from Complex Matrices: Results of the First International Proficiency Test

In the framework of the EU project EQuATox, a first international proficiency test (PT) on the detection and quantification of botulinum neurotoxins (BoNT) was conducted. Sample materials included BoNT serotypes A, B and E spiked into buffer, milk, meat extract and serum. Different methods were applied by the participants combining different principles of detection, identification and quantification. Based on qualitative assays, 95% of all results reported were correct. Successful strategies for BoNT detection were based on a combination of complementary immunological, MS-based and functional methods or on suitable functional in vivo/in vitro approaches (mouse bioassay, hemidiaphragm assay and Endopep-MS assay). Quantification of BoNT/A, BoNT/B and BoNT/E was performed by 48% of participating laboratories. It turned out that precise quantification of BoNT was difficult, resulting in a substantial scatter of quantitative data. This was especially true for results obtained by the mouse bioassay which is currently considered as "gold standard" for BoNT detection. The results clearly demonstrate the urgent need for certified BoNT reference materials and the development of methods replacing animal testing. In this context, the BoNT PT provided the valuable information that both the Endopep-MS assay and the hemidiaphragm assay delivered quantitative results superior to the mouse bioassay.

Recommended Immunological Strategies to Screen for Botulinum Neurotoxin-Containing Samples

Botulinum neurotoxins (BoNTs) cause the life-threatening neurological illness botulism in humans and animals and are divided into seven serotypes (BoNT/A–G), of which serotypes A, B, E, and F cause the disease in humans. BoNTs are classified as “category A” bioterrorism threat agents and are relevant in the context of the Biological Weapons Convention. An international proficiency test (PT) was conducted to evaluate detection, quantification and discrimination capabilities of 23 expert laboratories from the health, food and security areas. Here we describe three immunological strategies that proved to be successful for the detection and quantification of BoNT/A, B, and E considering the restricted sample volume (1 mL) distributed. To analyze the samples qualitatively and quantitatively, the first strategy was based on sensitive immunoenzymatic and immunochromatographic assays for fast qualitative and quantitative analyses. In the second approach, a bead-based suspension array was used for screening followed by conventional ELISA for quantification. In the third approach, an ELISA plate format assay was used for serotype specific immunodetection of BoNT-cleaved substrates, detecting the activity of the light chain, rather than the toxin protein. The results provide guidance for further steps in quality assurance and highlight problems to address in the future.

Results of a Saxitoxin Proficiency Test Including Characterization of Reference Material and Stability Studies

A saxitoxin (STX) proficiency test (PT) was organized as part of the Establishment of Quality Assurance for the Detection of Biological Toxins of Potential Bioterrorism Risk (EQuATox) project. The aim of this PT was to provide an evaluation of existing methods and the European laboratories’ capabilities for the analysis of STX and some of its analogues in real samples. Homogenized mussel material and algal cell materials containing paralytic shellfish poisoning (PSP) toxins were produced as reference sample matrices. The reference material was characterized using various analytical methods. Acidified algal extract samples at two concentration levels were prepared from a bulk culture of PSP toxins producing dinoflagellate Alexandrium ostenfeldii. The homogeneity and stability of the prepared PT samples were studied and found to be fit-for-purpose. Thereafter, eight STX PT samples were sent to ten participating laboratories from eight countries. The PT offered the participating laboratories the possibility to assess their performance regarding the qualitative and quantitative detection of PSP toxins. Various techniques such as official Association of Official Analytical Chemists (AOAC) methods, immunoassays, and liquid chromatography-mass spectrometry were used for sample analyses.

Simultaneous analysis of Alternaria toxins and citrinin in tomato: an optimised method using liquid chromatography-tandem mass spectrometry

Alternaria toxins and citrinin are mycotoxins produced by fungi growing on different raw materials and agricultural commodities. Maximum levels of these toxins in foods are currently under consideration by the European Commission as a risk management measure. In this study, a new quantitative method is described for the determination of five Alternaria toxins and citrinin in tomato and tomato juice samples based on LC-MS/MS detection. Samples were extracted with pure methanol, followed by a derivatisation step with 2,4-dinitrophenylhydrazine to improve the determination of tenuazonic acid and to decrease the wide polarity difference between the compounds of interest. Samples were purified on hydrophilic-modified styrene polymer solid-phase extraction cartridges. High-performance liquid chromatographic columns packed with different core-shell materials were tested for the separation of toxins and a C-18 phase was in the final method applied to achieve sufficient separation of all relevant analytes. A key element of this approach was to prove successful transferability of the method to three different triple quadrupole mass spectrometers. A full single laboratory method validation was performed on two LC-MS/MS systems and performance characteristics met the predefined requirements. Moreover, the method was used in an international proficiency test and the satisfactory z-scores obtained (-0.1 to 0.8 in tomato juice samples) demonstrated the reliability of the approach described. The method will be validated in an inter-laboratory collaborative study and if the criteria for method precision are met, the method will be proposed as a new Work Item to the European Committee for Standardisation.

Determination of total cadmium, lead, arsenic, mercury and inorganic arsenic in mushrooms: outcome of IMEP-116 and IMEP-39

The Institute for Reference Materials and Measurements (IRMM) of the Joint Research Centre (JRC), a Directorate General of the European Commission, operates the International Measurement Evaluation Program (IMEP). IMEP organises inter-laboratory comparisons in support of European Union policies. This paper presents the results of two proficiency tests (PTs): IMEP-116 and IMEP-39, organised for the determination of total Cd, Pb, As, Hg and inorganic As (iAs) in mushrooms. Participation in IMEP-116 was restricted to National Reference Laboratories (NRLs) officially appointed by national authorities in European Union member states. IMEP-39 was open to all other laboratories wishing to participate. Thirty-seven participants from 25 countries reported results in IMEP-116, and 62 laboratories from 36 countries reported for the IMEP-39 study. Both PTs were organised in support to Regulation (EC) No. 1881/2006, which sets the maximum levels for certain contaminants in food. The test item used in both PTs was a blend of mushrooms of the variety shiitake (Lentinula edodes). Five laboratories, with demonstrated measurement capability in the field, provided results to establish the assigned values (Xref). The standard uncertainties associated to the assigned values (uref) were calculated by combining the uncertainty of the characterisation (uchar) with a contribution for homogeneity (ubb) and for stability (ust), whilst uchar was calculated following ISO 13528. Laboratory results were rated with z- and zeta (ζ)-scores in accordance with ISO 13528. The standard deviation for proficiency assessment, σp, ranged from 10% to 20% depending on the analyte. The percentage of satisfactory z-scores ranged from 81% (iAs) to 97% (total Cd) in IMEP-116 and from 64% (iAs) to 84% (total Hg) in IMEP-39.

Standardization of Radon Measurements: II. Accuracy and Proficiency Testing

The accuracy of in situ environmental radon measurement techniques is reviewed and new data for charcoal canister, alpha-track (track-etch) and electret detectors are presented. Deficiencies reported at the 1987 meeting in Wurenlingen. Federal Republic of Germany, for measurements using charcoal detectors are confirmed by the new results. Accuracy and precision of the alpha-track measurements laboratory were better than in 1987. Electret detectors appear to provide a convenient, accurate, and precise system for the measurement of radon concentration. The need for comprehensive, "blind" proficiency-testing programs is discussed.