Interlaboratory Proficiency Testing Research Articles

Susceptibility testing of fish cell lines for virus isolation

Passage of cell cultures may adversely influence cell susceptibility to virus infection through selection of cell clones that thrive in vitro but may not necessarily display high sensitivity to virus infection. Susceptibility to a given virus can therefore vary not only between cell lines and laboratories, but also between lineages of the same cell line. To minimise the occurrence of false negatives in a cell culture based surveillance system, we have investigated methods, to select cell lineages that are relatively superior in their susceptibility to a panel of virus isolates. The procedures compare susceptibility between cell lines and between lineages within a laboratory and between laboratories (Inter-laboratory Proficiency Test). The objective being that the most sensitive cell line and lineages are routinely selected for diagnostic purposes. In comparing cell lines, we simulated “non-cell-culture-adapted” virus by propagating the virus in heterologous cell lines to the one tested. A stock of test virus was produced and stored at − 80 °C and tests were conducted biannually. This procedure becomes complicated when several cell lines are in use and does not account for variation among lineages. In comparing cell lineages, we increased the number of isolates of each virus, propagated stocks in a given cell line and tested all lineages of that line in use in the laboratory. Testing of relative cell line susceptibility between laboratories is carried out annually via the Inter-laboratory Proficiency Test (Ariel et al., in press), which is organised by the European Community Reference Laboratory for Fish Diseases (CRL) in Denmark. In the year 2000, infected organ material rather than cell-culture-adapted virus was included in the test, to approach a realistic assessment of the variability in cell sensitivity for surveillance purposes within a cell line and between laboratories. In terms of economic and practical considerations as well as attempting to approach a realistic test system, we suggest the optimal procedure for susceptibility testing of fish cell lines for virus isolation to be a combination of biannual tests within the laboratory to compare cell lineages combined with the Inter-laboratory Proficiency Test.

Comparison of the Q-fever complement fixation test and two commercial enzyme-linked immunosorbent assays for the detection of serum antibodies against Coxiella burnetii (Q-fever) in ruminants: Recommendations for use of serological tests on imported animals in New Zealand

AIM: To make valid recommendations on the use of serological test methods for the detection of serum antibodies in ruminants against Coxiella burnetii (Q-fever), by comparing the performance of the complement fixation test (CFT) and two ELISA, and by identifying reasons for discrepancies between the test methods. METHODS: A total of 73 serum samples from infected cattle, 69 from infected goats, and 100 samples from non-infected cattle and 57 samples from non-infected sheep, as well as 95 samples from infected cattle herds (mix of seropositive and seronegative samples), were tested using the CFT, the IDEXX ELISA (I-ELISA) and the Pourquier ELISA (P-ELISA). A mixed panel of 12 serum samples from sheep from inter-laboratory proficiency testing (proficiency panel) was also tested using the CFT and both ELISA, and further investigated using IgG- and IgM-specific ELISA. RESULTS: Generally, the two commercial ELISA were more sensitive than the CFT for the detection of infected ruminants. Good agreement between ELISA for positive and negative results was found for samples from the infected herd, while results for the positive panels varied between the two ELISA. For the total of the positive serum panels, the I-ELISA detected 95% of samples as positive or suspicious, while the P-ELISA detected only 81%. In the P-ELISA, more samples were considered suspicious (18%) than in the I-ELISA (14%). All sera from noninfected sheep and cattle tested negative in the serological test methods employed, except for one positive sample from a sheep in the P-ELISA. Further investigation revealed that a CFT-positive but ELISA-negative result was due to high IgM and low IgG reactivity. CONCLUSIONS: The two commercial ELISA were more sensitive than the CFT in all panels from infected ruminants. However, they could only detect IgG. The I-ELISA should be the serological test method of choice for cattle, sheep and goats for import testing of animals into New Zealand because it was more sensitive than the P-ELISA and was equally specific to the PELISA and the CFT. For other animal species, such as deer and camelids, the CFT should still be used since none of the ELISA has been evaluated for these species. This study has shown that the two commercial ELISA will detect the majority of infected ruminants but may miss animals that have not developed an IgG response.

Direct detection of alkylphosphonic acids in environmental matrices by proton coupled phosphorus NMR

A simple, convenient, and direct one-dimensional (1D) (31)P NMR technique is demonstrated for the detection of alkylphosphonic acids (marker of nerve agents). The results of detection were validated after conducting various in-house exercises. The confidence generated by this study was found very useful in detection of different alkylphosphonic acids spiked in various official interlaboratory proficiency tests conducted by Organisation for the Prohibition of Chemical Weapons (OPCW).

AC power & energy standard — NPLI measurement, calibration & testing

AC power & energy standard of National Physical Laboratory, India (NPLI) is responsible for maintenance of national measurement standard of ac power & energy and international traceability through intercomparisons. It serves as the basis for dissemination of traceability in measurement through high level calibration and measurement services to the various user organizations in the country. It also supports and helps the industries in improving the measurement assurance systems through interlaboratory proficiency testing (PT) program and in solving actual field problems. Power measurement at zero power factors using zero power factor standards is described as it is used in intercomparison. The performance of energy meters under the various influence quantities is described as a service to the industries.

International Interlaboratory Proficiency Testing Program for Measurement of Azole Antifungal Plasma Concentrations

An international interlaboratory proficiency testing program for the measurement of antifungal drugs was initiated in 2007. This first round was limited to azole antifungals: fluconazole, itraconazole and hydroxyitraconazole, voriconazole, and posaconazole. The results demonstrate the need for and utility of an ongoing proficiency testing program to further improve the analytical methods for routine patient management and clinical research.

Bluetongue virus: European Community proficiency test (2007) to evaluate ELISA and RT-PCR detection methods with special reference to pooling of samples

Bluetongue virus European Community national reference laboratories (BTV-EC-NRLs) participated in an inter-laboratory proficiency test in 2007. The aim of the inter-laboratory proficiency test was to determine the ability of laboratories to detect antibodies to a series of BTV serotypes by cELISA and to detect viral RNA in animals infected with the European strain of BTV-8 by RT-PCR. Both serum and EDTA blood sample were diluted in order to determine the sensitivity of the assays. All the cELISAs were ‘fit-for purpose’ to detect antibodies to the common BTV serotypes circulating in Europe and the real time RT-PCR assays were all capable of detecting BTV-8 RNA albeit with varying sensitivities. There were however inconsistencies in the ability of the gel-based PCR assays to detect BTV RNA. In addition, samples taken on the first day of viraemia and at the peak of viraemia from animals experimentally infected with BTV-8, were diluted to determine if the diluting of samples affected the ability of the Shaw et al. (Shaw, A.E., M., P., Alpar, H.O., Anthony, S., Darpel, K.E., Batten, C.A., Carpenter, S., Jones, H., Oura, C.A.L., King, D.P., Elliott, H., Mellor, P.S., Mertens, P.P.C., 2007. Development and validation of a real-time RT-PCR assay to detect genome bluetongue virus segment 1. Journal of Virological Methods) RT-PCR assay to detect BTV-RNA at these time-points. Results indicated that, if samples were taken at the onset of viraemia, diluting at 1/5 resulted in a reduced ability of the assay to detect BTV RNA in the diluted compared to the neat samples. Diluting samples taken at the peak of viraemia at 1/10 however resulted in no loss in sensitivity.

Evaluation of a multiresidue method for measuring fourteen chemical groups of pesticides in water by use of LC-MS-MS

European Council Directive 98/83/EC on the quality of water intended for human consumption brought a new challenge for water-quality control routine laboratories, mainly on pesticides analysis. Under the guidelines of ISO/IEC 17025:2005, a multiresidue method was developed, validated, implemented in routine, and studied with real samples during a one-year period. The proposed method enables routine laboratories to handle a large number of samples, since 28 pesticides of 14 different chemical groups can be quantitated in a single procedure. The method comprises a solid-phase extraction step and subsequent analysis by liquid chromatography-mass spectrometry (LC-MS-MS). The accuracy was established on the basis of participation in interlaboratory proficiency tests, with encouraging results (majority |z-score| <2), and the precision was consistently analysed over one year. The limits of quantitation (below 0.050 microg L(-1)) are in agreement with the enforced threshold value for pesticides of 0.10 microg L(-1). Overall method performance is suitable for routine use according to accreditation rules, taking into account the data collected over one year.

Development of Palm-Based Reference Materials for the Quantification of Fatty Acids Composition

Characterisation of fatty acids composition of three palm-based reference materials was carried out through inter-laboratory proficiency tests. Twelve laboratories collaborated in these tests and the fatty acids compositions of palm oil, palm olein and palm stearin were determined by applying the MPOB Test Methods p3.4:2004 and p3.5:2004. Determination of consensus values and their uncertainties were based on the acceptable statistical agreement of results obtained from the collaborating laboratories. The consensus values and uncertainties (%) for each palm oil reference material produced are listed as follows : 0.20% (C12:0), 1.66+/-0.05% (C14:0), 43.39+/-0.39% (C16:0), 0.14+/-0.06% (C16:1), 3.90+/-0.11% (C18:0), 40.95+/-0.23% (C18:1), 9.68+/-0.21% (C18:2), 0.16+/-0.07% (C18:3) and 0.31+/-0.08% (C20:0) for fatty acids composition of palm oil; 0.23+/-0.04% (C12:0), 1.02+/-0.04% (C14:0), 39.66+/-0.19% (C16:0), 0.18+/-0.07% (C16:1), 3.81+/-0.04% (C18:0), 44.01+/-0.08% (C18:1), 10.73+/-0.08% (C18:2), 0.20+/-0.06% (C18:3) and 0.34+/-0.04% (C20:0) for fatty acids composition of palm olein; and 0.20% (C12:0), 1.14+/-0.05% (C14:0), 49.42+/-0.25% (C16:0), 0.16+/-0.08% (C16:1), 4.15+/-0.10% (C18:0), 36.14+/-0.77% (C18:1), 7.95+/-0.29% (C18:2), 0.11+/-0.07% (C18:3) and 0.30+/-0.08% (C20:0) for fatty acids composition of palm stearin.

Palm-Based Standard Reference Materials for Iodine Value and Slip Melting Point

This work described study protocols on the production of Palm-Based Standard Reference Materials for iodine value and slip melting point. Thirty-three laboratories collaborated in the inter-laboratory proficiency tests for characterization of iodine value, while thirty-two laboratories for characterization of slip melting point. The iodine value and slip melting point of palm oil, palm olein and palm stearin were determined in accordance to MPOB Test Methods p3.2:2004 and p4.2:2004, respectively. The consensus values and their uncertainties were based on the acceptability of statistical agreement of results obtained from collaborating laboratories. The consensus values and uncertainties for iodine values were 52.63 +/- 0.14 Wijs in palm oil, 56.77 +/- 0.12 Wijs in palm olein and 33.76 +/- 0.18 Wijs in palm stearin. For the slip melting points, the consensus values and uncertainties were 35.6 +/- 0.3 degrees C in palm oil, 22.7 +/- 0.4 degrees C in palm olein and 53.4 +/- 0.2 degrees C in palm stearin. Repeatability and reproducibility relative standard deviations were found to be good and acceptable, with values much lower than that of 10%. Stability of Palm-Based Standard Reference Materials remained stable at temperatures of -20 degrees C, 0 degrees C, 6 degrees C and 24 degrees C upon storage for one year.

A Bayesian approach to assess data from radionuclide activity analyses in environmental samples

A Bayesian statistical approach is introduced to assess experimental data from the analyses of radionuclide activity concentration in environmental samples (low activities). A theoretical model has been developed that allows the use of known prior information about the value of the measurand (activity), together with the experimental value determined through the measurement. The model has been applied to data of the Inter-laboratory Proficiency Test organised periodically among Spanish environmental radioactivity laboratories that are producing the radiochemical results for the Spanish radioactive monitoring network. A global improvement of laboratories performance is produced when this prior information is taken into account. The prior information used in this methodology is an interval within which the activity is known to be contained, but it could be extended to any other experimental quantity with a different type of prior information available.

Integration of Atazanavir into an Existing Liquid Chromatography UV Method for Protease Inhibitors: Validation and Application

Atazanavir (ATV) is a widely used human immunodeficiency virus (HIV)-1 protease inhibitor (PI) that, like other approved PIs, has been considered as a candidate for therapeutic drug monitoring (TDM). To provide ATV assay results that can be applied to patient management through TDM, the assay would need to perform in a manner consistent with Clinical Laboratory Improvement Amendments (CLIA) standards. To quantitate ATV concentrations in human plasma, the authors added ATV to a previously published reversed-phase high-performance liquid chromatography (HPLC) method from their laboratory. Detection was effected with use of a photodiode-array detector (PDA) collecting spectra at 248 nm. This method allows for detection of ATV to a lower limit of quantitation of 0.05 microg/mL, with an intra-assay coefficient of variation (CV%) of 8.9% or less over 5 days of testing and an interassay CV% ranging from 1.4 to 6.4%. The assay has met passing requirements for interlaboratory proficiency testing for 2 years nationally and internationally, with accuracy within +/-15% over all test samples. During 2 years, more than 100 batches of analyses have been performed and have proved the method is rugged, specific, and accurate. This assay method is currently used in the authors' clinical research program in TDM.

Determination of Inorganic Arsenic(III) and Arsenic(V) in Water Samples by Ion Chromatography/Inductively Coupled Plasma-Mass Spectrometry

A method was validated for the direct determination of As(III) and As(V) in water samples by ion chromatography/inductively coupled plasma-mass spectrometry. Sample preservation required only dilution with a mobile phase containing a sufficient amount of ethylenediaminetetraacetic acid and acetic acid. Analyses of 6 certified reference materials (CRMs) of various water matrixes, including seawater, demonstrated good method accuracy. The matrixes included 2 natural water samples [National Institute of Standards and Technology Standard Reference Material (NIST SRM) 1643e and NIST SRM 1640], 1 fortified standard solution (TMDA-64), 1 fortified water sample (TM-DWS), and 2 seawater samples (CASS-4 and NASS-5). The sum of As(III) and As(V) in each CRM agreed with the respective certified value for the total amount of As within its stated uncertainty. Quantitative recoveries (96.7-102.1%) were obtained. Satisfactory results were achieved for intraday repeatability [relative standard deviation (RSD = 0.3-5.1%] and interday precision (RSD = 0.7-4.1%). In the study of fortified blanks and fortified CRMs, quantitative recoveries of As(III) and As(V) (92.5-102.6%) were obtained. Interconversion of As(III) and As(V) was not observed under the conditions of sample preservation. International comparability of analytical results was demonstrated by the analysis of 2 interlaboratory proficiency test samples, NY7011 and NY8511, from the New York State Department of Health.

Fit-for-purpose shellfish reference materials for internal and external quality control in the analysis of phycotoxins

The need for reference materials for quality control of analysis of foodstuffs has been stressed frequently. This has been particularly true in the phycotoxins field, where there is a great shortage of both pure calibration standards and reference materials. Worldwide there are very few independent bodies that produce certified reference materials for phycotoxins, the main producers currently being the National Research Council Canada and the Japanese Food Research Laboratory. Limited availability of contaminated shellfish and algae, as well as the time and knowledge necessary for the production of adequate reference materials, continuously lead to limited editions of certified reference materials and even more limited production of in-house reference materials. The restricted availability of in-house quality control materials promotes the rapid use of the limited certified reference materials, which in turn hampers the production of the suite of materials required globally for complete protection of public health. This paper outlines the various options that analysts can pursue in the use of reference materials for internal and external quality control, with a view to optimising the efforts of both reference materials users and reference materials producers. For this purpose, the logical sequence is reviewed from the discovery of a new bioactive compound in shellfish, through initial method development up to regulation for food safety purposes including accepted reference methods. Subsequently, the requirements for and efforts typically spent in the production and characterisation of laboratory reference materials, certified reference materials and other test materials used in inter-laboratory studies or proficiency testing, in the area of marine biotoxins are evaluated. Particular emphasis is put on practical advice for the preparation of in-house reference materials. The intricate link between reference material characterisation and method performance is outlined to give guidance on the appropriate in-house method validation in the rapidly developing field of phycotoxins.

Direct determination of acrylamide in food by gas chromatography–high-resolution time-of-flight mass spectrometry

Simple and rapid gas chromatographic (GC) method employing a high-resolution time-of-flight mass analyzer that enables direct analysis (no derivatization) of acrylamide in various heat-processed foodstuffs has been developed and validated. Co-isolation of acrylamide precursors such as sugars and asparagine, constituting the risk of results overestimation due to additional formation of analyte in hot GC injector, is avoided by the extraction with n-propanol followed by solvent exchange to acetonitrile (MeCN). Introduction of a novel purification strategy, dispersive solid phase extraction, based on addition of primary-secondary amine (PSA) sorbent into deffated extract in MeCN, provides a significant reduction of some abundant matrix co-extracts (mainly free fatty acids). Isotope dilution technique (d 3-acrylamide as an internal standard) is employed for compensation of potential target analyte losses and/or matrix-inducted chromatographic response enhancement. Limits of quantifications (LOQs) ranged between 15 and 40 μg kg −1 and recoveries were between 97 and 108% depending on the examined food matrix. The repeatability of measurements (expressed as relative standard deviation, R.S.D.) was as low as 1.9% for potato crisps containing acrylamide at a level of 1 mg kg −1. Slightly higher values (R.S.D. < 4.0%) were achieved for breakfast cereals and crisp bread with approximately 10 times lower content of this processing contaminant. Trueness of results generated by this new method was demonstrated via FAPAS ® (Food Analysis Performance Assessment Scheme) interlaboratory proficiency tests.

Performance characteristics of an analytical procedure for determining chloramphenicol residues in muscle tissue by gas chromatography–electron capture detection

Validation of an analytical method for determining chloramphenicol residues in muscle tissue by gas chromatography-electron capture detection (GC-ECD) was performed according to the latest European Union criteria for the analysis of veterinary drugs in food, laid down by Commission Decision 2002/657/EC. The method using the meta isomer of chloramphenicol as an internal standard proved to be very selective, specific to other related phenicols and accurate to within +3.6% at a concentration level of 8.9 microg/kg, as present in the certified reference material available. The correlation coefficient of the calibration curve was 0.9991. At all three fortification levels studied (0.3, 0.45 and 0.6 microg/kg), repeatability and intra-laboratory reproducibility were <8 and < or =9%, respectively. The decision limit (CCalpha) and detection capability (CCbeta) were 0.07 and 0.12 microg/kg, respectively. The validation results and the results of participation in an international inter-laboratory proficiency test indicate that the method presented is completely suited for regulatory control to screen and quantify chloramphenicol residues in various muscle tissues on a routine basis.

Study on Gas Chromatographic Separation on the Basis of the Results of Interlaboratory Comparison Examination and Proficiency Testing for Determination of Dioxins

In the analysis of dioxins (PCDDs, PCDFs and DL-PCBs) whose isomers in total are more than 400 using gas chromatography-mass spectrometry, it is essential to design a suitable gas chromatographic condition to separate the peaks to be measured from other peaks. For this purpose, the literature was surveyed at first to know the separation ability of recent liquid phases for gas chromatographic columns, followed by characterization of experimental data obtained from three interlaboratory testings. A statistical calculation was applied to the results mentioned above to distinguish the separated peaks from the overlapped ones. Confident results were obtained after rejecting data of the overlapped peaks.

Interlaboratory Proficiency Testing as a Tool for Improving Performance in Laboratories Diagnosing Bovine Mastitis

The National Veterinary and Food Research Institute (Finland) and the Veterinary Laboratories Agency of the Quality Assurance Unit, Department for Environment, Food and Rural Affairs, United Kingdom (previously the Ministry of Agriculture, Fisheries and Food) organized a proficiency testing program for laboratories analyzing veterinary mastitis samples. Three test samples with lyophilized strains of common aerobic bacteria were sent to the participating laboratories 7 times between 2000 and 2003. The participants returned 98% of the requested data. The overall performance of the laboratories varied from 63 to 93% in different testing rounds. All laboratories diagnosed Staphylococcus aureus and Escherichia coli correctly at every round. Improvement in diagnosing individual bacteria was observed for Staphylococcus epidermidis, Streptococcus dysgalactiae, Enterococcus spp. and Klebsiella spp. The overall performance of the laboratories improved with increased participation. The educational role of the program was important. Laboratories working in the veterinary field should implement a documented quality system covering all functions of the laboratory, as well as a planned quality assurance system.

Proficiency Testing of Growing Media, Soil Improvers, Soils, and Nutrient Solutions

At Applied Plant Research two (interlaboratory) proficiency tests for (peat‐based) growing media, soil improvers, soil, and nutrient solution were being organized; one for the national and one for the European methods. Data were compiled according to ISO 5725. Reports containing all data, where the laboratories were identified only by a reference number were being sent to each of the participants. In the national methods, no problems have been recognized in large variations of nitrate. It was suggested that the inexperience with the new European methods was a source of error.

Identification, validation, and clinical implementation of tumor-associated biomarkers to improve therapy concepts, survival, and quality of life of cancer patients: Tasks of the Receptor and Biomarker Group of the European Organization for Research and Treatment of Cancer

Guiding principles are provided and discussed on how to inform the physician scientist and cancer researcher about quality control systems to enable a consistent assessment of the clinical value of tumor-associated biomarkers. Next to cancer research itself, the Receptor and Biomarker Group of the European Organization for Research and Treatment of Cancer (RBG-EORTC) advises on methodologies, test kits and test reagents utilized for tumor biomarker determination. Tumor-associated biomarkers are important and clinically useful tools which can aid the early diagnosis of cancer, determine prognosis, predict therapy response, and monitor disease. With regard to clinical use of tumor-associated bio-markers, quality assessment and quality assurance programs of the RBG-EORTC are crucially important issues. Test reagents, assays, and procedures for tumor sample collection and handling should be standardized. Furthermore, standard operating procedures (SOPs) should be developed for each type of tumor specimen. Assay formats and the quality of the tumor biomarker assay results have to be monitored by continuous within- and inter-laboratory proficiency testing. With this approach, a major step forward in the knowledge and understanding of the biological role and the clinical utility of tumor-associated biomarkers would be anticipated.

Improved sample preparation to determine acrylamide in difficult matrixes such as chocolate powder, cocoa, and coffee by liquid chromatography tandem mass spectroscopy.

An improved sample preparation (extraction and cleanup) is presented that enables the quantification of low levels of acrylamide in difficult matrixes, including soluble chocolate powder, cocoa, coffee, and coffee surrogate. Final analysis is done by isotope-dilution liquid chromatography-electrospray ionization tandem mass spectrometry (LC-MS/MS) using d3-acrylamide as internal standard. Sample pretreatment essentially encompasses (a) protein precipitation with Carrez I and II solutions, (b) extraction of the analyte into ethyl acetate, and (c) solid-phase extraction on a Multimode cartridge. The stability of acrylamide in final extracts and in certain commercial foods and beverages is also reported. This approach provided good performance in terms of linearity, accuracy and precision. Full validation was conducted in soluble chocolate powder, achieving a decision limit (CCalpha) and detection capability (CCbeta) of 9.2 and 12.5 microg/kg, respectively. The method was extended to the analysis of acrylamide in various foodstuffs such as mashed potatoes, crisp bread, and butter biscuit and cookies. Furthermore, the accuracy of the method is demonstrated by the results obtained in three inter-laboratory proficiency tests.