Interlaboratory Comparison Tests Research Articles

Do’s and don’ts of microplastic research: a comprehensive guide

Microplastics are environmental contaminants consisting of small plastics ≤ 5 mm. Concerns over the adverse effects of microplastics have led to a rapid growth in the available literature despite the lack of harmonized methods and materials. Therefore, the field is becoming increasingly daunting to new researchers. A state-of-the-art guide was assembled following a comprehensive literature review of microplastics research with the intent of addressing contemporary challenges, prioritized based on a survey, and introducing best practices. The lack of standardized methods and reference materials, the lack of access to analytical equipment, and the difficulty in working with lower environmental concentrations in laboratory tests (e.g., toxicity assays) remain a great challenge. The present work addresses these issues across three main sections: definitions, sampling, and evaluation of adverse effects. Harmonized methods and greater collaboration were identified as opportunities in this rapidly evolving field. A review of available interlaboratory comparison tests was also conducted to support additional recommendations.

The Research on interlaboratory comparison test of LED lighting products

The article introduces the Interlaboratory Comparison (IC) test for three different types of light emitting diode (LED) lamps measurement about the key photometric, colorimetric, and electrical parameters. The article analyses the deviations of the test results between the reference values and test results from six participating laboratories. It found that the photometric and colorimetric parameters showed high deviations between the reference values and participating laboratories’ test results. The recommended participating laboratory improvement measures in the article are as follows: checking the traceability of standard artefacts, checking data correction, improving test procedures, checking ambient temperature, checking calculation software, and checking the response of the photodetector, etc.

Rapid X-ray fluorescence analysis as a modern alternative to traditional spectral methods in geochemical prospecting

The purpose of the study is to present the research results of the capabilities of modern portable rapid X-ray fluorescence analyzers when solving problems of geological and geochemical prospecting. On example of the applied SciAps X200 analyzer, the metrological indicators for the analysis results by portable instruments have been studied. The accuracy assessment results of analytical studies according to state standard reference samples are shown. Reproducibility of the analysis results is calculated on the basis of samples from promising gold sites of the Bodaibo synclinorium. The method is proved to be of high precision, and measurement errors in many cases are many times lower than the permissible certified values. The reproducibility is shown as 0,5–20 % depending on the element, which in most cases is significantly lower than the methodology permits. The results of interlaboratory comparative tests confirming the comparability of the analytical results of stationary and portable X-ray fluorescence analyzers are presented. For a number of significant elements, the authors have substantiated the lack of need to refine the results of the field rapid X-ray fluorescence analysis using labor-intensive and expensive methods with acid decomposition - atomic emission and atomic absorption spectroscopy. It has been proved that introduction of portable express equipment into geological prospecting works will make it possible to conduct real-time “on site” analytical studies.

Determination of Trace Perchlorate in Soil using Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)

The international standard (IS) currently used for determining perchlorate in soil is not applicable to trace perchlorate. We developed a quantitative analysis method using liquid chromatography–tandem mass spectrometry (LC-MS/MS) for the trace perchlorate in soil. The perchlorate was extracted from air-dried soil (<150 μm) with distilled water. We proposed the optimum extraction method that included mechanical shaking followed by centrifugation. An internal standard material (Cl18O4-) was added to the extracts and standard solutions at concentration of 5 μg L-1. The samples were analyzed by LC-MS/MS equipped with a reversed phase C18 column packed with core-shell particles containing trimethylsilane functional groups. Samples that may be interfered with organic matter present in the soil should be purified with a C18 cartridge. The method detection limit and limit of quantitation for our method was 1.31 and 4.36 μg/kg, respectively. We verified the proposed method through interlaboratory comparison test; both coefficients of variation for repeatability (CVr) and reproducibility (CVR) were less than 5%. Therefore, we concluded that the proposed method may be used for precise quantitative analysis of trace amounts of perchlorate in soil.

The effect of the volume of tests and the number of participants on the assessment of qualification in interlaboratory comparison tests

The results of a comparative analysis of statistical indicators for assessing the proficiency determined during interlaboratory comparison tests (ICT) are presented. The main statistical indicators were selected: the assigned value, standard deviation for assessment the proficiency and standard uncertainty of the assigned value. Statistical indicators were determined in accordance with Algorithm A, GOST R 50779.60. Comparison of the indicators was carried out on the basis of numerical experiment data (random number generation) for the ultimate tensile strength of a D16AT aluminum alloy depending on the number of samples and the number of participants in the ICT qualification program. The calculation and subsequent statistical analysis of the proficiency test scores was based on the values generated by the software. Random number generation is performed for a characteristic that has a normal distribution law with the parameters of the mean equal to 450 MPa and standard deviation equal to 5 MPa. The values of the normal distribution parameters chosen as an example corresponded to the average level of tensile strength values of standard specimens made of D16AT aluminum alloy sheets. The numerical experiment (generation of random values) was carried out for given cases of the number of participants and the number of proficiency testing samples (PTS) independently of each other using separate samples of the appropriate size. A total of 36,000 ultimate tensile strength values were generated for the proficiency testing samples made of D16AT aluminum alloy sheets. As a result of calculations, 48 average values were determined (according to the number of considered implementations of ICT programs, depending on the number of participants and the proficiency testing samples) for each selected statistical indicator of the ICT qualification program. The average value of each statistical indicator was determined on samples with a bulk of 250 to 2000 generated (experimental) values, depending on the number of participants and the number of proficiency testing samples. The analysis thus performed made it possible to evaluate the influence of the volume of tests and the number of participants on the assessment of the proficiency in interlaboratory comparative tests. It is shown that for the selected range of the number of ICT participants (from 5 to 20) and the number of PTS (from 5 to 10), the value of the assigned xpt value does not depend either on the number of tested PTS or the number of ICT participants. The maximum discrepancy between the assigned value and the given level of tensile strength (450 MPa) is 0.13%, which falls within the error (rounding) for this level of values and cannot lead to significant errors in proficiency testing during ICT. The standard deviation for the qualification assessment, regardless of the number of participants, decreases with an increase in the number of proficiency testing samples, but such a decrease is insignificant and does not exceed the standard deviation (SD) value of the ultimate tensile strength (for the selected model for generating experimental values, the SD value is accepted to be 5 MPa). In contrast to the assigned value and the standard deviation for the qualification assessment, it is shown that the standard uncertainty of the assigned value for the ultimate tensile strength of standard samples made of D16AT aluminum alloy sheets depends on the number of participants and the number of proficiency testing samples tested by each participant and decreases with an increase in the number of participants in ICT programs and the number of proficiency testing samples.

109 Inter- and Intra-Laboratory Comparison of 6 Dustiness Testing Methods: Towards the Development of an OECD Testing Guideline

Abstract Dustiness is a key parameter describing the ability of powder materials to generate dust during agitation. The main goal of this work was to generate and assess the scientific basis for the validation and applicability of 6 dustiness methods to nanomaterials, and development of a subsequent OECD testing guideline. Six dustiness methods (rotating drum, small rotating drum, continuous drop, vortex shaker, fluidizer and venturi) were subjected to an intra- and inter-laboratory comparison (ILC) in which 15 international laboratories participated. ILC tests were conducted for 6 materials (3 TiO2 and 3 SiO2) of different chemical natures and dustiness levels. Each participating laboratory conducted at least 3 replicates per material. Harmonization of procedures, methods and data treatment took place prior to testing. Results from the ILC were assessed considering the different reported metrics such as respirable mass and particle number dustiness index. Overall, the intralaboratory variability for the different methods and metrics was under 30%. Variation between laboratories was generally higher for respirable mass than particle number dustiness index. These variations were mostly attributed to differences in setups such as tubing length or instrumentation. All methods except the venturi, which was characteristic for presenting low differences between materials and opposed classification to the rest of the methods, showed relatively similar material ranking. For all methods and laboratories the calculated z-score (measure of the deviation of each laboratory from the true value) was <2 as based on ISO 13528, which indicates gratifying results. Funding: EU H2020 Research and Innovation Programme under Grant Agreement 814401.

Preventing Mislabeling: A Comparative Chromatographic Analysis for Classifying Medical and Industrial Cannabis.

Gas chromatography (GC) techniques for analyzing and determining the cannabinoid profile in cannabis (Cannabis sativa L.) are widely used in standard laboratories; however, these methods may mislabel the profile when used under rapid conditions. Our study aimed to highlight this problem and optimize GC column conditions and mass spectrometry (MS) parameters to accurately identify cannabinoids in both standards and forensic samples. The method was validated for linearity, selectivity, and precision. It was observed that when tetrahydrocannabinol (Δ9-THC) and cannabidiolic acid (CBD-A) were examined using rapid GC conditions, the resulting derivatives generated identical retention times. Wider chromatographic conditions were applied. The linear range for each compound ranged from 0.02 μg/mL to 37.50 μg/mL. The R2 values ranged from 0.996 to 0.999. The LOQ values ranged from 0.33 μg/mL to 5.83 μg/mL, and the LOD values ranged from 0.11 μg/mL to 1.92 μg/mL. The precision values ranged from 0.20% to 8.10% RSD. In addition, forensic samples were analyzed using liquid chromatography (HPLC-DAD) in an interlaboratory comparison test, with higher CBD and THC content than GC-MS determination (p < 0.05) in samples. Overall, this study highlights the importance of optimizing GC techniques to avoid mislabeling cannabinoids in cannabis samples.

Interlaboratory experiment design in the production of reference materials (ICRM) and statistical processing of the results obtained

Institute for Certified Reference Materials (ICRM) is a leading manufacturer of certified reference materi­als (CRM) for ferrous metallurgy. The entire process of CRM production from the purchase of a material to the certificate issuance takes about two years. The determination of the metrological characteristics is the longest stage of CRM production. The metrological characteristics of reference materials, are evaluated, as a rule, according to the results of an interlaboratory experiment and, in addition, in combination with a comparison method. The interlaboratory experiment arranged by ICRM, involves at least 10 competent analytical laboratories. The interlaboratory comparative tests are also carried out to test the qualification of laboratories. Since 2017, ICRM has been accredited by the Federal Accreditation Service as a profi­ciency provider of interlaboratory comparison.

Evaluation of the quality of measurements of the testing laboratory during interlaboratory comparative tests

The article presents the statistical processing of the test results of the mass fraction of the chlorine ion (Cl) obtained from two accredited testing laboratories. The stages of statistical processing of the results of interlaboratory comparison tests are as follows: elimination of gross errors, determination of the uniformity of the sample, calculation of the assigned value, evaluation of the quality of the measurement results. The presence of gross errors in the sample was determined by the Grubbs test, and the uniformity of the sample was confirmed by the Fisher’s test and Student’s test. The assigned value was calculated by a robust method using algorithm A with an iterative scale. The quality of laboratory measurement results was evaluated using the z-score. The z-score value for each participant showed that the results of measuring the mass fraction of chlorine ion in cement samples were acceptable. The quality of the results of these laboratories is satisfactory and does not require corrective measures. These results of the test quality assessment can be used for the organizers of interlaboratory tests, as well as for accredited laboratories that check their qualifications.

Challenges in measuring nitrogen isotope signatures in inorganic nitrogen forms: An interlaboratory comparison of three common measurement approaches.

RationaleStable isotope approaches are increasingly applied to better understand the cycling of inorganic nitrogen (Ni) forms, key limiting nutrients in terrestrial and aquatic ecosystems. A systematic comparison of the accuracy and precision of the most commonly used methods to analyze δ15N in NO3 − and NH4 + and interlaboratory comparison tests to evaluate the comparability of isotope results between laboratories are, however, still lacking.MethodsHere, we conducted an interlaboratory comparison involving 10 European laboratories to compare different methods and laboratory performance to measure δ15N in NO3 − and NH4 +. The approaches tested were (a) microdiffusion (MD), (b) chemical conversion (CM), which transforms Ni to either N2O (CM‐N2O) or N2 (CM‐N2), and (c) the denitrifier (DN) methods.ResultsThe study showed that standards in their single forms were reasonably replicated by the different methods and laboratories, with laboratories applying CM‐N2O performing superior for both NO3 − and NH4 +, followed by DN. Laboratories using MD significantly underestimated the “true” values due to incomplete recovery and also those using CM‐N2 showed issues with isotope fractionation. Most methods and laboratories underestimated the at%15N of Ni of labeled standards in their single forms, but relative errors were within maximal 6% deviation from the real value and therefore acceptable. The results showed further that MD is strongly biased by nonspecificity. The results of the environmental samples were generally highly variable, with standard deviations (SD) of up to ± 8.4‰ for NO3 − and ± 32.9‰ for NH4 +; SDs within laboratories were found to be considerably lower (on average 3.1‰). The variability could not be connected to any single factor but next to errors due to blank contamination, isotope normalization, and fractionation, and also matrix effects and analytical errors have to be considered.ConclusionsThe inconsistency among all methods and laboratories raises concern about reported δ15N values particularly from environmental samples.

UJI BANDING ANTAR LABORATORIUM DALAM RANGKA PENINGKATAN KEPERCAYAAN TERHADAP LABORATORIUM PENGUJIAN FISIS POLITEKNIK ATK

One of the raw materials for footwear is Chrome tanned box leather with a thickness according to the applicable SNI quality standards. The problem with measuring skin thickness has received less attention from laboratory personnel during testing. The Quality Control Section is responsible for the implementation of quality assurance and quality control of test results. External quality control is carried out by cross-laboratory comparisons. The purpose of this research is to find out the competence of the Physical Testing laboratory as an executor in inter-laboratory comparison tests with skin thickness test parameters. The material used is cow leather. The test method uses SNI-06-7128-2005. stationary. The comparative test was carried out from June to August 2022 followed by the Physical Testing Laboratory as the executor of the activities (laboratory A), laboratories B and C. The test results obtained standard deviation for laboratory A vs B 0.1396 and laboratory A vs C 0.0795 . The t value for laboratory A vs B was 0.625 and laboratory A vs C was 1.85. Based on t table at 95% confidence level for laboratory A vs B 2.228 and laboratory Avs C 2.201, t count &lt; from t table comparative test between laboratories is declared not significantly different or acceptable. Physical Testing laboratory personnel can be declared competent for the skin thickness test.

The features of the evaluation of the results of experimental data in interlaboratory comparison tests for low-cycle fatigue

Improving the efficiency of assessing the results of low-cycle fatigue (LCF) test in the course of interlaboratory comparison tests (ICT) requires a reduction of the uncertainty associated with a number of random factors independent on the quality of testing and qualification of testing laboratories. Those factors are attributed to a random nature of the initiation and development of the fatigue fracture due to the inhomogeneity of the macro- and microstructure of the material, the state of the sample surface, stress concentrator, etc. A method for evaluating the results of LCF tests at ICT is presented. The method is implemented on the basis of linear regression analysis of experimental values of the mean and standard deviation of the logarithm of the durability at a given stress level. The features of evaluating the results of experimental data of interlaboratory comparison tests for low-cycle fatigue are presented. We propose to use the median estimate of the logarithm of fatigue life (corresponding to a given level (amplitude) of stresses obtained from the median fatigue curve constructed from the results of statistical analysis including regression analysis of the variances of experimental data) as an assigned value for assessing the characteristics of functioning of the laboratories participating in the ICT. The assigned value and estimates of the performance of laboratories is obtained using the median fatigue curve, which is plotted depending on the number of participants in the ICT. With a small number of participants, the median low-cycle fatigue curve is plotted according to the test results obtained by the expert laboratory, whereas for a sufficiently large number of participants according to the test results combined for all laboratories participating in the ICT.

Development of a certified reference material intended to control measurement results accuracy of petroleum products in water and its application for proficiency testing of laboratories through interlaboratory comparative tests

The article considers the notion of oil content as a measurable indicator and provides information on the procedures for measuring the content of petroleum products by IR spectrometry in natural water, drinking water, and treated wastewater. Certified reference materials (CRMs) for petroleum products with certified characteristics of the mass or mass concentration of petroleum products in the matrix were registered in the system of metrological support of measurements. The content of polar petroleum products in the raw material was not taken into account when establishing the certified values of these CRMs; this leads to a significant difference between a certified characteristic of CRMs and the determined indicator of measurement procedures based on the IR spectrometry method. In contrast to CRMs with a certified characteristic in the form of the total content of petroleum products, there was a need to develop CRM for determining the mass concentration of only non-polar and low-polar petroleum products by the IR spectrometry method.Information about the stages of CRM development is presented: selection and preparation of material, investigation of material stability. The results of CRM certification for certified indicators in the range of 0.05–2.00 mg/dm3 are presented. The correctness of these results was confirmed in accredited laboratories by interlaboratory comparative tests.The CRM of mass concentration of non-polar petroleum products in a polar organic solvent GSO 11733–2021 was approved. The metrological characteristics of the CRM were established: the range of permissible certified values is 0.1–3.0 mg/cm3, the permissible relative expanded uncertainty of the certified value for k=2 5 %. The traceability to SI units of the certified CRM value is insured.It has been confirmed that the developed GSO 11733–2021 is intended to control the accuracy of the measurement results of the mass concentration of non-polar petroleum products in drinking water, natural surface water, and treated wastewater using IR spectrometry and can be used for attestation of procedures for measuring the mass concentration of non-polar petroleum products in water by IR spectrometry. The scope of the CRM is environmental protection, quality control of drinking water, natural surface water, and treated wastewater.

Improving the quality of meat and canned products by production technology

This article provides an overview of qualification testing programs, inter-laboratory comparative tests and qualification testing in testing laboratories that analyze the safety of canned meat products. Organoleptic, physico-chemical, safety and microbiological studies were conducted, comparing Semipalatinsk canned meat products with other samples. According to the results of the study, the company's products turned out to be positive. It is proved that the main task is to produce high-quality products in order to meet the requirements of consumers. At the enterprise for the production of canned meat, measures were envisaged to ensure high-quality and safe products in accordance with the requirements of standards. The regulatory and technical requirements used by the enterprise in the production of canned meat were analyzed. In the market economy of the Republic of Kazakhstan, the development of individual entrepreneurship should be at a stable level in the food industry.

Study of P-Phenylenediamine (PPD) Concentrations after Hair Dye Mixing: A Call for Safety Reassessment

Para-phenylenediamine (PPD) is a chemical that is widely used in hair dyes. Multiple safety and regulatory agencies have categorized PPD as a potent sensitizer. In addition, PPD has carcinogenicity and genotoxicity attributes and, consequently, it is regulated at a maximal concentration of 2.0%. The aim of this study was to test whether the limit for PPD is surplus, and hence whether the consumer may be exposed to unnecessarily PPD levels. Experimentally, the analysis of PPD was performed using HPLC, where method validation and an inter-laboratory comparison test (ILC) were conducted to evaluate method performance. Thirty-three commercial products were analyzed, and five products were chosen to study the unconsumed PPD. Successfully, the implemented method confirmed its suitability and validity for the determination of PPD. For ILC results, PPD levels were 0.97 ± 0.04% and 0.92 ± 0.02%, quantified by our laboratory and an accredited laboratory, respectively. For all products, the initial concentration (T0) of PPD was lower than the regulatory limit. After 45 min, the content of PPD significantly reduced compared to T0. One product showed unconsumed PPD to be as high as 96% following the recommended dyeing time. In conclusion, the existence of high levels of unreacted PPD increases the likelihood of allergic events and elevates the risk of PPD-related chemicals. Collaborative efforts between industries, regulatory bodies, and health-related decision makers are deemed necessary to establish safe concentrations for PPD.

Interlaboratory Validation of Toxicity Testing Using the Duckweed Lemna minor Root-Regrowth Test.

Simple SummaryDuckweed (Lemna minor) is commonly used as a phytotoxicity test organism, adopted by the main international standardization organizations (ISO, OECD, USEPA, ASTM). For duckweed tests, measurements of fronds or biomass are usually preferred with a standard exposure period of at least 7 days. The proposed root- regrowth test differs from other internationally standardized methods in several important aspects: (a) the test can be performed within 72 h; (b) the test vessel was a 24-well cell plate; (c) the required volume of test water samples was 3 mL; (d) roots were excised before exposure and newly developed roots then measured. The validation of the new test method by interlaboratory comparison tests confirmed that the Lemna root bioassay is valid and reliable. The root growth test is therefore a valuable tool for rapid toxicity screening of wastewater effluents and hazardous pollutants in natural waters because it is simple to perform, quick to conduct, cost-effective to operate, and can have operational benefits for testing time, since management decisions need to be made promptly in the event of unpredictable pollution events.The common duckweed (Lemna minor), a freshwater monocot that floats on the surfaces of slow-moving streams and ponds, is commonly used in toxicity testing. The novel Lemna root- regrowth test is a toxicity test performed in replicate test vessels (24-well plates), each containing 3 mL test solution and a 2–3 frond colony. Prior to exposure, roots are excised from the plant, and newly developed roots are measured after 3 days of regrowth. Compared to the three internationally standardized methods, this bioassay is faster (72 h), simpler, more convenient (requiring only a 3-mL) and cheaper. The sensitivity of root regrowth to 3,5-dichlorophenol was statistically the same as using the conventional ISO test method. The results of interlaboratory comparison tests conducted by 10 international institutes showed 21.3% repeatability and 27.2% reproducibility for CuSO4 and 21.28% repeatability and 18.6% reproducibility for wastewater. These validity criteria are well within the generally accepted levels of <30% to 40%, confirming that this test method is acceptable as a standardized biological test and can be used as a regulatory tool. The Lemna root regrowth test complements the lengthier conventional protocols and is suitable for rapid screening of wastewater and priority substances spikes in natural waters.

DEVELOPMENT OF APPROACHES TO LABORATORY CONTROL OF «BIOTESTLAB» LTD TO ENSURE QUALITY OF VETERINARY PREPARATIONS

The article presents the development of approaches to laboratory control and the results of research related to the standardization of methods at Ltd "BIOTESTLAB" to ensure the quality of veterinary drugs. Attention is paid to the methods of biological quality control of veterinary drugs: microbiological purity, hemagglutination reaction (HAR), determination of infectious activity of embryonic vaccines. Because such methods are characterized by low automation, low accuracy, the impact on the result of error due to personnel performing operations manually, the lack of regulatory approaches to validation of methods. The influence on the reliability of the obtained results on determining the titer of infectious activity of the virus of the following factors: quality and concentration of the applied suspension of erythrocytes of a rooster, duration of cultivation of a virus, technique of performance by the controller of each operation of a technique is investigated. Studies on the influence of these factors were conducted on the example of determining the titer of infectious activity of Newcastle disease virus. Approaches to accounting for the obtained results by the method of qualitative HAR, namely visual control of hemagglutination reaction on glass and on a plate are established. A comparative characterization of the results for the detection of hem agglutinin of Newcastle disease virus on glass (using 2% suspension of erythrocytes) and on the plate (using 1% suspension of erythrocytes). The results of inter-laboratory comparative tests of microbiological methods conducted to verify the qualification and reliability of the results are presented. It is demonstrated that the proper organization of laboratory control in measures to confirm the results of control of quantitative methods and evaluation of biological material by standardizing methods, conducting internal laboratory testing and participation in inter-laboratory comparative tests ensures and guarantees the quality of veterinary drugs.

Inter-laboratory Comparisons and Their Roles in Accreditation

Results of interlaboratory comparisons and proficiency tests are a significant parameter for the calibration and testing laboratories for assuring the quality of test and calibration results performed by those laboratories. If test and calibration laboratories want to demonstrate that they operate according to a management system, that they are technically competent and that they can produce technically valid results in the tests and calibrations they perform for their customers, the general requirements they must meet are defined in ISO/IEC 17025:2017. This international standard forms the basis of international laboratory accreditation. Clause 7.7 Ensuring the validity of results in this standard requires laboratories to establish the procedures and instructions and other technical documentation needed to ensure the results of the tests and calibrations they perform. Participation in inter-laboratory comparison or proficiency testing programs is one of the most important of these activities. Participation in inter-laboratory comparisons provides an opportunity for laboratories to independently evaluate their analytical performance, both in absolute terms and in comparison, to other techniques. In this study, information about calibration laboratories and accreditation activities is given and the importance of inter-laboratory comparison studies is explained to ensure the results of the measurements made by calibration laboratories.

АНАЛИЗ ОПЫТА УЧАСТИЯ В МЕЖЛАБОРАТОРНЫХ СРАВНИТЕЛЬНЫХ ИСПЫТАНИЯХ ЛАБОРАТОРИЙ РАДИАЦИОННОГО КОНТРОЛЯ В НАЦИОНАЛЬНОЙ СИСТЕМЕ АККРЕДИТАЦИИ

Purpose: Formation of the idea of laboratories accredited by Accreditation System of Russian Federation, in particular radiation control laboratories, about the possibility of confirming technical competence by means of participation in interlaboratory comparison tests at international level.&#x0D; Content: Description of the experience of successful passing the international comparisons by radiation control laboratories under up-to-date requirements.&#x0D; Conclusion: The experience described in the article can be used by accredited laboratories in practice for conformity validation with accreditation criteria.

Interlaboratory comparison of SARS-CoV2 molecular detection assays in use by U.S. veterinary diagnostic laboratories.

The continued search for intermediate hosts and potential reservoirs for SARS-CoV2 makes it clear that animal surveillance is critical in outbreak response and prevention. Real-time RT-PCR assays for SARS-CoV2 detection can easily be adapted to different host species. U.S. veterinary diagnostic laboratories have used the CDC assays or other national reference laboratory methods to test animal samples. However, these methods have only been evaluated using internal validation protocols. To help the laboratories evaluate their SARS-CoV2 test methods, an interlaboratory comparison (ILC) was performed in collaboration with multiple organizations. Forty-four sets of 19 blind-coded RNA samples in Tris-EDTA (TE) buffer or PrimeStore transport medium were shipped to 42 laboratories. Results were analyzed according to the principles of the International Organization for Standardization (ISO) 16140-2:2016 standard. Qualitative assessment of PrimeStore samples revealed that, in approximately two-thirds of the laboratories, the limit of detection with a probability of 0.95 (LOD95) for detecting the RNA was ≤20 copies per PCR reaction, close to the theoretical LOD of 3 copies per reaction. This level of sensitivity is not expected in clinical samples because of additional factors, such as sample collection, transport, and extraction of RNA from the clinical matrix. Quantitative assessment of Ct values indicated that reproducibility standard deviations for testing the RNA with assays reported as N1 were slightly lower than those for N2, and they were higher for the RNA in PrimeStore medium than those in TE buffer. Analyst experience and the use of either a singleplex or multiplex PCR also affected the quantitative ILC test results.