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36 results on '"Uhlig, Steffen"'

1. Conformity assessment of processes and lots in the framework of JCGM 106:2012

Author

Göb, Rainer, Uhlig, Steffen, and Colson, Bernard

Subjects
Statistics - Applications
Abstract

ISO/IEC 17000:2020 defines conformity assessment as an "activity to determine whether specified requirements relating to a product, process, system, person or body are fulfilled". JCGM (2012) establishes a framework for accounting for measurement uncertainty in conformity assessment. The focus of JCGM (2012) is on the conformity assessment of individual units of product based on measurements on a cardinal continuous scale. However, the scheme can also be applied to composite assessment targets like finite lots of product or manufacturing processes, and to the evaluation of characteristics in discrete cardinal or nominal scales. We consider the application of the JCGM scheme in the conformity assessment of finite lots or processes of discrete units subject to a dichotomous quality classification as conforming and nonconforming. A lot or process is classified as conforming if the actual proportion nonconforming does not exceed a prescribed upper tolerance limit, otherwise the lot or process is classified as nonconforming. The measurement on the lot or process is a statistical estimation of the proportion nonconforming based on attributes or variables sampling, and meassurement uncertainty is sampling uncertainty. Following JCGM (2012), we analyse the effect of measurement uncertainty (sampling uncertainty) in attributes sampling, and we calculate key conformity assessment parameters, in particular the producer's and consumer's risk. We suggest to integrate such parameters as a useful add-on into ISO acceptance sampling standards such as the ISO 2859 series., Comment: 27 pages, 6 figures

Published
2024

2. LASSO extension: using the number of non-zero coefficients to test the global model hypothesis

Author

Uhlig, Carsten and Uhlig, Steffen

Subjects
Statistics - Methodology, Quantitative Biology - Quantitative Methods
Abstract

In this paper, we propose a test procedure based on the LASSO methodology to test the global null hypothesis of no dependence between a response variable and $p$ predictors, where $n$ observations with $n < p$ are available. The proposed procedure is similar to the F-test for a linear model, which evaluates significance based on the ratio of explained to unexplained variance. However, the F-test is not suitable for models where $p \geq n$. This limitation is due to the fact that when $p \geq n$, the unexplained variance is zero and thus the F-statistic can no longer be calculated. In contrast, the proposed extension of the LASSO methodology overcomes this limitation by using the number of non-zero coefficients in the LASSO model as a test statistic after suitably specifying the regularization parameter. The method allows reliable analysis of high-dimensional datasets with as few as $n = 40$ observations. The performance of the method is tested by means of a power study., Comment: 9 pages, 2 figures

Published
2023

11. Successful Detection of Delta and Omicron Variants of SARS-CoV-2 by Veterinary Diagnostic Laboratory Participants in an Interlaboratory Comparison Exercise

Author

Deng, Kaiping, primary, Nemser, Sarah M, additional, Frost, Kirstin, additional, Goodman, Laura B, additional, Ip, Hon S, additional, Killian, Mary Lea, additional, Ulaszek, Jodie, additional, Kiener, Shannon, additional, Kmet, Matthew, additional, Uhlig, Steffen, additional, Hettwer, Karina, additional, Colson, Bertrand, additional, Nichani, Kapil, additional, Schlierf, Anja, additional, Tkachenko, Andriy, additional, Miller, Megan R, additional, Reddy, Ravinder, additional, and Tyson, Gregory H, additional

Published
2023
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14. Successful Detection of Delta and Omicron Variants of SARS-CoV-2 by Veterinary Diagnostic Laboratory Participants in an Interlaboratory Comparison Exercise

Author

Deng, Kaiping, primary, Nemser, Sarah M., additional, Frost, Kirstin, additional, Goodman, Laura B., additional, Ip, Hon S., additional, Killian, Mary Lea, additional, Ulaszek, Jodie, additional, Kiener, Shannon, additional, Kmet, Matthew, additional, Uhlig, Steffen, additional, Hettwer, Karina, additional, Colson, Bertrand, additional, Nichani, Kapil, additional, Schlierf, Anja, additional, Tkachenko, Andriy, additional, Miller, Megan R., additional, Reddy, Ravinder, additional, and Tyson, Gregory H., additional

Published
2022
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15. A Procedure for Estimating Fundamental Variability

Author

Uhlig, Steffen, Colson, Bertrand, and Gowik, Petra

Subjects
analytical_chemistry
Abstract

The question whether a given set of test items can be considered “identical” is often addressed in terms of the homogeneity of the test material from which said items were taken. However, for some types of matrices – in particular, for matrices consisting of minute separate particles, only some of which carry the analyte under consideration – even in the case of homogenous test material, an irreducible source of variability between test items may remain: the fundamental variability. In this paper, the concept of fundamental variability is explained, and procedures for reducing and characterizing it are described.

Published
2022

16. Measurement Uncertainty Interval In Case of a Known Relationship between Precision and Mean

Author

Uhlig, Steffen, Colson, Bertrand, and Gowik, Petra

Subjects
life_sciences_other
Abstract

Measurement uncertainty is typically expressed in terms of a symmetric interval , where denotes the measurement result and the expanded uncertainty. However, in the case of heteroscedasticity, symmetric uncertainty intervals can be misleading. In this paper, a different approach for the calculation of uncertainty intervals is introduced. This approach is applicable when a validation study has been conducted with samples with known concentrations. It will be shown how, under certain circumstances, asymmetric uncertainty intervals arise quite naturally and lead to more reliable uncertainty intervals.

Published
2022

17. Second round of an interlaboratory comparison of SARS-CoV2 molecular detection assays used by 45 veterinary diagnostic laboratories in the United States

Author

Deng, Kaiping, primary, Uhlig, Steffen, additional, Goodman, Laura B., additional, Ip, Hon S., additional, Killian, Mary Lea, additional, Nemser, Sarah M., additional, Ulaszek, Jodie, additional, Kiener, Shannon, additional, Kmet, Matthew, additional, Frost, Kirstin, additional, Hettwer, Karina, additional, Colson, Bertrand, additional, Nichani, Kapil, additional, Schlierf, Anja, additional, Tkachenko, Andriy, additional, Mlalazi-Oyinloye, Mothomang, additional, Scott, Andrew, additional, Reddy, Ravinder, additional, and Tyson, Gregory H., additional

Published
2022
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19. Application of the Bayesian Conformity Assessment Framework from JCGM 106:2012 for Lot Inspection on the Basis of Single Items

Author

Colson, Bertrand, Uhlig, Steffen, Göb, Rainer, and Gowik, Petra

Subjects
life_sciences_other
Abstract

The ISO 2859 and ISO 3951 series provide acceptance sampling procedures for lot inspection, allowing both sample size and acceptance rule to be determined, starting from a specific value either for the consumer or producer risk. However, insufficient resources often make it difficult to implement “ISO sampling plans.” In cases where the sample size is determined by external constraints, the focus shifts from determining sample size to determining consumer and producer risks. Moreover, if the sample size is very low (e.g. one single item), prior information should be included in the statistical analysis. For this reason, it makes sense to work within a Bayesian theoretical framework, such as that described in JCGM 106. Accordingly, the approach from JCGM 106 is adopted and broadened so as to allow application to lot inspection. The discussion is based on a “real-life” example of lot inspection on the basis of a single item. Starting from simple assumptions, expressions for both the prior and posterior distributions are worked out, and it is shown how the concepts from JCGM 106 can be reinterpreted in the context of lot inspection. Conceptual differences regarding the definition of consumer and producer risks in JCGM 106 and in the ISO acceptance sampling standards are elucidated and a numerical example is provided.

Published
2022

20. Diagnostic Potential of Exosomal microRNAs in Colorectal Cancer

Author

Dohmen, Jonas, primary, Semaan, Alexander, additional, Kobilay, Makbule, additional, Zaleski, Martin, additional, Branchi, Vittorio, additional, Schlierf, Anja, additional, Hettwer, Karina, additional, Uhlig, Steffen, additional, Hartmann, Gunther, additional, Kalff, Jörg C., additional, Matthaei, Hanno, additional, Lingohr, Philipp, additional, and Holdenrieder, Stefan, additional

Published
2022
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24. Interlaboratory Validation of a DNA Metabarcoding Assay for Mammalian and Poultry Species to Detect Food Adulteration

Author

Dobrovolny, Stefanie, Uhlig, Steffen, Frost, Kirstin, Schlierf, Anja, Nichani, Kapil, Simon, Kirsten, Cichna-Markl, Margit, and Hochegger, Rupert

Subjects
validation, interlaboratory ring trial, Health (social science), DNA metabarcoding, animal species, species identification, NGS, food adulteration, Plant Science, Health Professions (miscellaneous), Microbiology, Food Science
Abstract

Meat species authentication in food is most commonly based on the detection of genetic variations. Official food control laboratories frequently apply single and multiplex real-time polymerase chain reaction (PCR) assays and/or DNA arrays. However, in the near future, DNA metabarcoding, the generation of PCR products for DNA barcodes, followed by massively parallel sequencing by next generation sequencing (NGS) technologies, could be an attractive alternative. DNA metabarcoding is superior to well-established methodologies since it allows simultaneous identification of a wide variety of species not only in individual foodstuffs but even in complex mixtures. We have recently published a DNA metabarcoding assay for the identification and differentiation of 15 mammalian species and six poultry species. With the aim to harmonize analytical methods for food authentication across EU Member States, the DNA metabarcoding assay has been tested in an interlaboratory ring trial including 15 laboratories. Each laboratory analyzed 16 anonymously labelled samples (eight samples, two subsamples each), comprising six DNA extract mixtures, one DNA extract from a model sausage, and one DNA extract from maize (negative control). Evaluation of data on repeatability, reproducibility, robustness, and measurement uncertainty indicated that the DNA metabarcoding method is applicable for meat species authentication in routine analysis.

Published
2022

26. Second round of the interlaboratory comparison (ILC) exercise of SARS-CoV-2 molecular detection assays being used by 45 veterinary diagnostic laboratories in the US

Author

Deng, Kaiping, primary, Uhlig, Steffen, additional, Goodman, Laura B., additional, Ip, Hon S., additional, Killian, Mary Lea, additional, Nemser, Sarah M., additional, Ulaszek, Jodie, additional, Kiener, Shannon, additional, Kmet, Matthew, additional, Frost, Kirstin, additional, Hettwer, Karina, additional, Colson, Bertrand, additional, Nichani, Kapil, additional, Schlierf, Anja, additional, Tkachenko, Andriy, additional, Mlalazi-Oyinloye, Mothomang, additional, Scott, Andrew, additional, Reddy, Ravinder, additional, and Tyson, Gregory H., additional

Published
2022
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27. Synergistic Adverse Effects of Azithromycin and Hydroxychloroquine on Human Cardiomyocytes at a Clinically Relevant Treatment Duration

Author

Li, Wener, primary, Luo, Xiaojing, additional, Poetsch, Mareike S., additional, Oertel, Reinhard, additional, Nichani, Kapil, additional, Schneider, Martin, additional, Strano, Anna, additional, Hasse, Marcel, additional, Steiner, Robert-Patrick, additional, Cyganek, Lukas, additional, Hettwer, Karina, additional, Uhlig, Steffen, additional, Simon, Kirsten, additional, Guan, Kaomei, additional, and Schubert, Mario, additional

Published
2022
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28. sj-pdf-1-vdi-10.1177_10406387221115702 – Supplemental material for Second round of an interlaboratory comparison of SARS-CoV2 molecular detection assays used by 45 veterinary diagnostic laboratories in the United States

Author

Deng, Kaiping, Uhlig, Steffen, Goodman, Laura B., Ip, Hon S., Killian, Mary Lea, Nemser, Sarah M., Ulaszek, Jodie, Kiener, Shannon, Kmet, Matthew, Frost, Kirstin, Hettwer, Karina, Colson, Bertrand, Nichani, Kapil, Schlierf, Anja, Tkachenko, Andriy, Mlalazi-Oyinloye, Mothomang, Scott, Andrew, Reddy, Ravinder, and Tyson, Gregory H.

Subjects
70706 Veterinary Medicine, FOS: Clinical medicine, FOS: Veterinary sciences, 111599 Pharmacology and Pharmaceutical Sciences not elsewhere classified
Abstract

Supplemental material, sj-pdf-1-vdi-10.1177_10406387221115702 for Second round of an interlaboratory comparison of SARS-CoV2 molecular detection assays used by 45 veterinary diagnostic laboratories in the United States by Kaiping Deng, Steffen Uhlig, Laura B. Goodman, Hon S. Ip, Mary Lea Killian, Sarah M. Nemser, Jodie Ulaszek, Shannon Kiener, Matthew Kmet, Kirstin Frost, Karina Hettwer, Bertrand Colson, Kapil Nichani, Anja Schlierf, Andriy Tkachenko, Mothomang Mlalazi-Oyinloye, Andrew Scott, Ravinder Reddy and Gregory H. Tyson in Journal of Veterinary Diagnostic Investigation

Published
2022
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31. Challenging the “gold standard” of colony-forming units - Validation of a multiplex real-time PCR for quantification of viable Campylobacter spp. in meat rinses

Author

Stingl, Kerstin, primary, Heise, Janine, additional, Thieck, Maja, additional, Wulsten, Imke F., additional, Pacholewicz, Ewa, additional, Iwobi, Azuka N., additional, Govindaswamy, Janani, additional, Zeller-Péronnet, Véronique, additional, Scheuring, Sandra, additional, Luu, Huong Quynh, additional, Fridriksdottir, Vala, additional, Gölz, Greta, additional, Priller, Florian, additional, Gruntar, Igor, additional, Jorgensen, Frieda, additional, Koene, Miriam, additional, Kovac, Jasna, additional, Lick, Sonja, additional, Répérant, Elisabeth, additional, Rohlfing, Annika, additional, Zawilak-Pawlik, Anna, additional, Rossow, Marko, additional, Schlierf, Anja, additional, Frost, Kirstin, additional, Simon, Kirsten, additional, Uhlig, Steffen, additional, and Huber, Ingrid, additional

Published
2021
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33. Development of Non-Targeted Mass Spectrometry Method for Distinguishing Spelt and Wheat.

Author

Nichani, Kapil, Uhlig, Steffen, Colson, Bertrand, Hettwer, Karina, Simon, Kirsten, Bönick, Josephine, Uhlig, Carsten, Kemmlein, Sabine, Stoyke, Manfred, Gowik, Petra, Huschek, Gerd, and Rawel, Harshadrai M.

Subjects
FLOUR, MASS spectrometry, BREAD, WHEAT, CONVOLUTIONAL neural networks, FRAUD investigation, FRAUD
Abstract

Food fraud, even when not in the news, is ubiquitous and demands the development of innovative strategies to combat it. A new non-targeted method (NTM) for distinguishing spelt and wheat is described, which aids in food fraud detection and authenticity testing. A highly resolved fingerprint in the form of spectra is obtained for several cultivars of spelt and wheat using liquid chromatography coupled high-resolution mass spectrometry (LC-HRMS). Convolutional neural network (CNN) models are built using a nested cross validation (NCV) approach by appropriately training them using a calibration set comprising duplicate measurements of eleven cultivars of wheat and spelt, each. The results reveal that the CNNs automatically learn patterns and representations to best discriminate tested samples into spelt or wheat. This is further investigated using an external validation set comprising artificially mixed spectra, samples for processed goods (spelt bread and flour), eleven untypical spelt, and six old wheat cultivars. These cultivars were not part of model building. We introduce a metric called the D score to quantitatively evaluate and compare the classification decisions. Our results demonstrate that NTMs based on NCV and CNNs trained using appropriately chosen spectral data can be reliable enough to be used on a wider range of cultivars and their mixes. [ABSTRACT FROM AUTHOR]

Published
2023
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34. Interlaboratory comparison of SARS-CoV2 molecular detection assays in use by U.S. veterinary diagnostic laboratories.

Author

Deng, Kaiping, Uhlig, Steffen, Ip, Hon S., Lea Killian, Mary, Goodman, Laura B., Nemser, Sarah, Ulaszek, Jodie, Pickens, Shannon, Newkirk, Robert, Kmet, Matthew, Frost, Kirstin, Hettwer, Karina, Colson, Bertrand, Nichani, Kapil, Schlierf, Anja, Tkachenko, Andriy, Reddy, Ravinder, and Reimschuessel, Renate

Subjects
SARS-CoV-2, REVERSE transcriptase polymerase chain reaction, STANDARD deviations, VETERINARY hospitals, GOVERNMENT laboratories, LABORATORIES, TESTING laboratories
Abstract

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. [ABSTRACT FROM AUTHOR]

Published
2021
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36. Essential terminology and considerations for validation of non-targeted methods.

Author

Nichani K, Uhlig S, Stoyke M, Kemmlein S, Ulberth F, Haase I, Döring M, Walch SG, and Gowik P

Abstract

Through their suggestive name, non-targeted methods (NTMs) do not aim at a predefined "needle in the haystack." Instead, they exploit all the constituents of the haystack. This new type of analytical method is increasingly finding applications in food and feed testing. However, the concepts, terms, and considerations related to this burgeoning field of analytical testing need to be propagated for the benefit of those associated with academic research, commercial development, or official control. This paper addresses frequently asked questions regarding terminology in connection with NTMs. The widespread development and adoption of these methods also necessitate the need to develop innovative approaches for NTM validation, i.e., evaluating the performance characteristics of a method to determine if it is fit-for-purpose. This work aims to provide a roadmap for approaching NTM validation. In doing so, the paper deliberates on the different considerations that influence the approach to validation and provides suggestions therefor., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2022 The Author(s).)

Published
2022
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