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Schenk J, Abrams S, Litzroth A, Cornelissen L, Grammens T, Theeten H, Hens N. Identifying immunity gaps for measles using Belgian serial serology data. Vaccine 2022; 40:3676-3683. [PMID: 35589453 PMCID: PMC9108896 DOI: 10.1016/j.vaccine.2022.05.009] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2022] [Revised: 04/21/2022] [Accepted: 05/04/2022] [Indexed: 11/29/2022]
Abstract
Vaccine-preventable diseases, such as measles, have been re-emerging in countries with moderate to high vaccine uptake. It is increasingly important to identify and close immunity gaps and increase coverage of routine childhood vaccinations, including two doses of the measles-mumps-rubella vaccine (MMR). Here, we present a simple cohort model relying on a Bayesian approach to evaluate the evolution of measles seroprevalence in Belgium using the three most recent cross-sectional serological survey data collections (2002, 2006 and 2013) and information regarding vaccine properties. We find measles seroprevalence profiles to be similar for the different regions in Belgium. These profiles exhibit a drop in seroprevalence in birth cohorts that were offered vaccination at suboptimal coverages in the first years after routine vaccination has been started up. This immunity gap is observed across all cross-sectional survey years, although it is more pronounced in survey year 2013. At present, the COVID-19 pandemic could negatively impact the immunization coverage worldwide, thereby increasing the need for additional immunization programs in groups of children that are impacted by this. Therefore, it is now even more important to identify existing immunity gaps and to sustain and reach vaccine-derived measles immunity goals.
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Affiliation(s)
- Julie Schenk
- Data Science Institute, Interuniversity Institute for Biostatistics and Statistical Bioinformatics (I-BioStat), UHasselt, Diepenbeek, Belgium.
| | - Steven Abrams
- Data Science Institute, Interuniversity Institute for Biostatistics and Statistical Bioinformatics (I-BioStat), UHasselt, Diepenbeek, Belgium,Global Health Institute (GHI), Family Medicine and Population Health (FAMPOP), University of Antwerp, Wilrijk, Belgium
| | - Amber Litzroth
- Service of Epidemiology of Infectious Diseases, Scientific Directorate of Epidemiology and Public Health, Sciensano, Brussels, Belgium
| | - Laura Cornelissen
- Service of Epidemiology of Infectious Diseases, Scientific Directorate of Epidemiology and Public Health, Sciensano, Brussels, Belgium
| | - Tine Grammens
- Service of Epidemiology of Infectious Diseases, Scientific Directorate of Epidemiology and Public Health, Sciensano, Brussels, Belgium
| | - Heidi Theeten
- Centre for Evaluation of Vaccination (CEV), Vaccine and Infectious Disease Institute, University of Antwerp, Wilrijk, Belgium,Public Health and Surveillance Department, Zorg en Gezondheid Vlaanderen, Belgium
| | - Niel Hens
- Data Science Institute, Interuniversity Institute for Biostatistics and Statistical Bioinformatics (I-BioStat), UHasselt, Diepenbeek, Belgium,Centre for Health Economics Research and Modelling Infectious Diseases (CHERMID), Vaccine and Infectious Disease Institute, University of Antwerp, Wilrijk, Belgium
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2
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Amirgazin A, Shevtsov A, Karibayev T, Berdikulov M, Kozhakhmetova T, Syzdykova L, Ramankulov Y, Shustov AV. Highly pathogenic avian influenza virus of the A/H5N8 subtype, clade 2.3.4.4b, caused outbreaks in Kazakhstan in 2020. PeerJ 2022; 10:e13038. [PMID: 35256921 PMCID: PMC8898005 DOI: 10.7717/peerj.13038] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2021] [Accepted: 02/09/2022] [Indexed: 01/11/2023] Open
Abstract
Background Large poultry die-offs happened in Kazakhstan during autumn of 2020. The birds' disease appeared to be avian influenza. Northern Kazakhstan was hit first and then the disease propagated across the country affecting eleven provinces. This study reports the results of full-genome sequencing of viruses collected during the outbreaks and investigation of their relationship to avian influenza virus isolates in the contemporary circulation in Eurasia. Methods Samples were collected from diseased birds during the 2020 outbreaks in Kazakhstan. Initial virus detection and subtyping was done using RT-PCR. Ten samples collected during expeditions to Northern and Southern Kazakhstan were used for full-genome sequencing of avian influenza viruses. Phylogenetic analysis was used to compare viruses from Kazakhstan to viral isolates from other world regions. Results Phylogenetic trees for hemagglutinin and neuraminidase show that viruses from Kazakhstan belong to the A/H5N8 subtype and to the hemagglutinin H5 clade 2.3.4.4b. Deduced hemagglutinin amino acid sequences in all Kazakhstan's viruses in this study contain the polybasic cleavage site (KRRKR-G) indicative of the highly pathogenic phenotype. Building phylogenetic trees with the Bayesian phylogenetics results in higher statistical support for clusters than using distance methods. The Kazakhstan's viruses cluster with isolates from Southern Russia, the Russian Caucasus, the Ural region, and southwestern Siberia. Other closely related prototypes are from Eastern Europe. The Central Asia Migratory Flyway passes over Kazakhstan and birds have intermediate stops in Northern Kazakhstan. It is postulated that the A/H5N8 subtype was introduced with migrating birds. Conclusion The findings confirm the introduction of the highly pathogenic avian influenza viruses of the A/Goose/Guangdong/96 (Gs/GD) H5 lineage in Kazakhstan. This virus poses a tangible threat to public health. Considering the results of this study, it looks justifiable to undertake measures in preparation, such as install sentinel surveillance for human cases of avian influenza in the largest pulmonary units, develop a human A/H5N8 vaccine and human diagnostics capable of HPAI discrimination.
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Affiliation(s)
- Asylulan Amirgazin
- National Center for Biotechnology, Nur-Sultan, Akmola Region, Kazakhstan
| | - Alexandr Shevtsov
- National Center for Biotechnology, Nur-Sultan, Akmola Region, Kazakhstan
| | - Talgat Karibayev
- National Reference Veterinary Center, Nur-Sultan, Akmola Region, Kazakhstan
| | - Maxat Berdikulov
- National Reference Veterinary Center, Nur-Sultan, Akmola Region, Kazakhstan
| | | | - Laura Syzdykova
- National Center for Biotechnology, Nur-Sultan, Akmola Region, Kazakhstan
| | - Yerlan Ramankulov
- National Center for Biotechnology, Nur-Sultan, Akmola Region, Kazakhstan,National Laboratory Astana, Nazarbayev University, Nur-Sultan, Akmola Region, Kazakhstan
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3
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Foster PG. Phylogenetic Analysis That Models Compositional Heterogeneity over the Tree. Methods Mol Biol 2022; 2569:119-135. [PMID: 36083446 DOI: 10.1007/978-1-0716-2691-7_6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Molecular sequences in a phylogenetic analysis can differ in composition, and that shows that the process of evolution can change over time. However, models of evolution in common use are homogeneous over the tree, and if used in a phylogenetic analysis with compositionally tree-heterogeneous datasets these models can recover incorrect trees. The NDCH or Node-Discrete Compositional Heterogeneity model is able to model such data by accommodating differences in composition over the tree. Usage, problems, and limitations of this model are discussed, and a modification, the NDCH2 model, is described that can ameliorate some of these problems and limitations. Using these models can greatly increase the fit of the model to the data and can find better tree topologies. These models and various statistical tests are illustrated using a bacterial SSU rRNA dataset. These models are implemented in the software P4, and files for the analyses described here are made available.
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Affiliation(s)
- Peter G Foster
- Department of Life Sciences, Natural History Museum, London, UK
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4
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Abstract
Species tree inference from multilocus data has emerged as a powerful paradigm in the postgenomic era, both in terms of the accuracy of the species tree it produces as well as in terms of elucidating the processes that shaped the evolutionary history. Bayesian methods for species tree inference are desirable in this area as they have been shown not only to yield accurate estimates, but also to naturally provide measures of confidence in those estimates. However, the heavy computational requirements of Bayesian inference have limited the applicability of such methods to very small data sets. In this article, we show that the computational efficiency of Bayesian inference under the multispecies coalescent can be improved in practice by restricting the space of the gene trees explored during the random walk, without sacrificing accuracy as measured by various metrics. The idea is to first infer constraints on the trees of the individual loci in the form of unresolved gene trees, and then to restrict the sampler to consider only resolutions of the constrained trees. We demonstrate the improvements gained by such an approach on both simulated and biological data.
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Affiliation(s)
- Yaxuan Wang
- Computer Science Department, Rice University, Houston, TX
| | - Huw A Ogilvie
- Computer Science Department, Rice University, Houston, TX
| | - Luay Nakhleh
- Computer Science Department, Rice University, Houston, TX
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5
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Abstract
Background Bayesian MCMC has become a common approach for phylogenetic inference. But the growing size of molecular sequence data sets has created a pressing need to improve the computational efficiency of Bayesian phylogenetic inference algorithms. Results This paper develops a new algorithm to improve the efficiency of Bayesian phylogenetic inference for models that include a per-branch rate parameter. In a Markov chain Monte Carlo algorithm, the presented proposal kernel changes evolutionary rates and divergence times at the same time, under the constraint that the implied genetic distances remain constant. Specifically, the proposal operates on the divergence time of an internal node and the three adjacent branch rates. For the root of a phylogenetic tree, there are three strategies discussed, named Simple Distance, Small Pulley and Big Pulley. Note that Big Pulley is able to change the tree topology, which enables the operator to sample all the possible rooted trees consistent with the implied unrooted tree. To validate its effectiveness, a series of experiments have been performed by implementing the proposed operator in the BEAST2 software. Conclusions The results demonstrate that the proposed operator is able to improve the performance by giving better estimates for a given chain length and by using less running time for a given level of accuracy. Measured by effective samples per hour, use of the proposed operator results in overall mixing more efficient than the current operators in BEAST2. Especially for large data sets, the improvement is up to half an order of magnitude.
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Affiliation(s)
- Rong Zhang
- School of Computer Science, University of Auckland, Auckland, New Zealand.
| | - Alexei Drummond
- School of Computer Science, University of Auckland, Auckland, New Zealand.,School of Biological Sciences, University of Auckland, Auckland, New Zealand
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6
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Nakamura M, Wakano JY, Aoki K, Kobayashi Y. The popularity spectrum applied to a cross-cultural question. Theor Popul Biol 2019; 133:104-116. [PMID: 31672615 DOI: 10.1016/j.tpb.2019.10.003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 09/13/2019] [Accepted: 10/21/2019] [Indexed: 10/25/2022]
Abstract
We investigate a new approach for identifying the contribution of horizontal transmission between groups to cross-cultural similarity. This method can be applied to datasets that record the presence or absence of artefacts, or attributes thereof, in archaeological and ethnographic assemblages, from which popularity spectra can be constructed. Based on analytical and simulation models, we show that the form of such spectra is sensitive to horizontal transmission between groups. We then fit the analytical model to existing datasets by Bayesian MCMC and obtain evidence for strong horizontal transmission in oceanic as opposed to continental datasets. We check the validity of our statistical method by using individual-based models, and show that the vertical transmission rate tends to be underestimated if the datasets are obtained from lattice-structured rather than island-structured meta-populations. We also suggest that there may be more borrowing of functional than stylistic traits, although the evidence for this is currently ambiguous.
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Affiliation(s)
- Mitsuhiro Nakamura
- Organization for the Strategic Coordination of Research and Intellectual Properties, Meiji University, Nakano 4-21-1, Nakano-ku, Tokyo 164-8525, Japan
| | - Joe Yuichiro Wakano
- School of Interdisciplinary Mathematical Sciences, Meiji University, Nakano 4-21-1, Nakano-ku, Tokyo 164-8525, Japan
| | - Kenichi Aoki
- Organization for the Strategic Coordination of Research and Intellectual Properties, Meiji University, Nakano 4-21-1, Nakano-ku, Tokyo 164-8525, Japan
| | - Yutaka Kobayashi
- School of Economics and Management, Kochi University of Technology, 2-22 Eikokuji, Kochi City, Kochi 780-8515, Japan.
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7
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Mahikul W, White LJ, Poovorawan K, Soonthornworasiri N, Sukontamarn P, Chanthavilay P, Pan-Ngum W, Medley GF. A Population Dynamic Model to Assess the Diabetes Screening and Reporting Programs and Project the Burden of Undiagnosed Diabetes in Thailand. Int J Environ Res Public Health 2019; 16:E2207. [PMID: 31234452 DOI: 10.3390/ijerph16122207] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/04/2019] [Revised: 05/29/2019] [Accepted: 05/30/2019] [Indexed: 01/07/2023]
Abstract
Diabetes mellitus (DM) is rising worldwide, exacerbated by aging populations. We estimated and predicted the diabetes burden and mortality due to undiagnosed diabetes together with screening program efficacy and reporting completeness in Thailand, in the context of demographic changes. An age and sex structured dynamic model including demographic and diagnostic processes was constructed. The model was validated using a Bayesian Markov Chain Monte Carlo (MCMC) approach. The prevalence of DM was predicted to increase from 6.5% (95% credible interval: 6.3-6.7%) in 2015 to 10.69% (10.4-11.0%) in 2035, with the largest increase (72%) among 60 years or older. Out of the total DM cases in 2015, the percentage of undiagnosed DM cases was 18.2% (17.4-18.9%), with males higher than females (p-value < 0.01). The highest group with undiagnosed DM was those aged less than 39 years old, 74.2% (73.7-74.7%). The mortality of undiagnosed DM was ten-fold greater than the mortality of those with diagnosed DM. The estimated coverage of diabetes positive screening programs was ten-fold greater for elderly compared to young. The positive screening rate among females was estimated to be significantly higher than those in males. Of the diagnoses, 87.4% (87.0-87.8%) were reported. Targeting screening programs and good reporting systems will be essential to reduce the burden of disease.
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8
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Osada Y, Yamakita T, Shoda-Kagaya E, Liebhold AM, Yamanaka T. Disentangling the drivers of invasion spread in a vector-borne tree disease. J Anim Ecol 2018; 87:1512-1524. [PMID: 30010199 DOI: 10.1111/1365-2656.12884] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 06/05/2018] [Indexed: 11/30/2022]
Abstract
Pine wilt disease (PWD) invaded southern Japan in the early 1900s and has gradually expanded its range to northern Honshu (Japanese mainland). The disease is caused by a pathogenic North American nematode, which is transmitted by native pine sawyer beetles. Recently, the disease has invaded other portions of East Asia and Europe where extensive mortality of host pines is anticipated to resemble historical patterns seen in Japan. There is a critical need to identify the main drivers of PWD invasion spread so as to predict the future spread and evaluate containment strategies in newly invaded world regions. But the coupling of pathogen and vector population dynamics introduces considerable complexity that is important for understanding this and other plant disease invasions. In this study, we analysed historical (1980-2011) records of PWD infection and vector abundance, which were spatially extensive but recorded at coarse categorical levels (none, low and high) across 403 municipalities in northern Honshu. We employed a multistate occupancy model that accounted both for demographic stochasticity and observation errors in categorical data. Analysis revealed that sparse sawyer populations had lower probabilities of transition to high abundance than did more abundant populations even when regional abundance stayed the same, suggesting the existence of positive density dependence, that is an Allee effect, in sawyer dynamics. Climatic conditions (average accumulated degree days) substantially limited invasion spread in northern regions, but this climatic influence on sawyer dynamics was generally weaker than the Allee effect. Our results suggest that tactics (eg sanitation logging of infected pines) which strengthen Allee effects in sawyer dynamics may be effective strategies for slowing the spread of PWD.
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Affiliation(s)
- Yutaka Osada
- Graduate School of Life Sciences, Tohoku University, Miyagi, Japan
| | - Takehisa Yamakita
- R&D Center for Submarine Resources, Japan Agency for Marine-Earth Science and Technology, Yokohama, Japan
| | - Etsuko Shoda-Kagaya
- Department of Forest Entomology, Forestry and Forest Products Research Institute, Forest Research and Management Organization, Tsukuba, Japan
| | - Andrew M Liebhold
- US Forest Service Northern Research Station, Morgantown, West Virginia
| | - Takehiko Yamanaka
- Statistical Modeling Unit, Institute for Agro-Environmental Sciences, NARO, Tsukuba, Japan
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9
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Zhu YO, Aw PPK, de Sessions PF, Hong S, See LX, Hong LZ, Wilm A, Li CH, Hue S, Lim SG, Nagarajan N, Burkholder WF, Hibberd M. Single-virion sequencing of lamivudine-treated HBV populations reveal population evolution dynamics and demographic history. BMC Genomics 2017; 18:829. [PMID: 29078745 PMCID: PMC5660452 DOI: 10.1186/s12864-017-4217-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Accepted: 10/16/2017] [Indexed: 01/22/2023] Open
Abstract
BACKGROUND Viral populations are complex, dynamic, and fast evolving. The evolution of groups of closely related viruses in a competitive environment is termed quasispecies. To fully understand the role that quasispecies play in viral evolution, characterizing the trajectories of viral genotypes in an evolving population is the key. In particular, long-range haplotype information for thousands of individual viruses is critical; yet generating this information is non-trivial. Popular deep sequencing methods generate relatively short reads that do not preserve linkage information, while third generation sequencing methods have higher error rates that make detection of low frequency mutations a bioinformatics challenge. Here we applied BAsE-Seq, an Illumina-based single-virion sequencing technology, to eight samples from four chronic hepatitis B (CHB) patients - once before antiviral treatment and once after viral rebound due to resistance. RESULTS With single-virion sequencing, we obtained 248-8796 single-virion sequences per sample, which allowed us to find evidence for both hard and soft selective sweeps. We were able to reconstruct population demographic history that was independently verified by clinically collected data. We further verified four of the samples independently through PacBio SMRT and Illumina Pooled deep sequencing. CONCLUSIONS Overall, we showed that single-virion sequencing yields insight into viral evolution and population dynamics in an efficient and high throughput manner. We believe that single-virion sequencing is widely applicable to the study of viral evolution in the context of drug resistance and host adaptation, allows differentiation between soft or hard selective sweeps, and may be useful in the reconstruction of intra-host viral population demographic history.
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Affiliation(s)
- Yuan O Zhu
- Genome Institute of Singapore, Singapore, 138672, Singapore.
| | - Pauline P K Aw
- Genome Institute of Singapore, Singapore, 138672, Singapore
| | | | - Shuzhen Hong
- Genome Institute of Singapore, Singapore, 138672, Singapore
| | - Lee Xian See
- Institute of Molecular and Cell Biology, Singapore, 138673, Singapore
| | - Lewis Z Hong
- Institute of Molecular and Cell Biology, Singapore, 138673, Singapore
| | - Andreas Wilm
- Genome Institute of Singapore, Singapore, 138672, Singapore
| | - Chen Hao Li
- Genome Institute of Singapore, Singapore, 138672, Singapore
| | - Stephane Hue
- London School of Hygiene and Tropical Medicine, London, UK
| | - Seng Gee Lim
- National University Hospital, Singapore, 119074, Singapore
| | | | | | - Martin Hibberd
- Genome Institute of Singapore, Singapore, 138672, Singapore.,London School of Hygiene and Tropical Medicine, London, UK
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10
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Agogo GO, van der Voet H, van ’t Veer P, Ferrari P, Muller DC, Sánchez-Cantalejo E, Bamia C, Braaten T, Knüppel S, Johansson I, van Eeuwijk FA, Boshuizen HC. A method for sensitivity analysis to assess the effects of measurement error in multiple exposure variables using external validation data. BMC Med Res Methodol 2016; 16:139. [PMID: 27737637 PMCID: PMC5064985 DOI: 10.1186/s12874-016-0240-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Accepted: 10/05/2016] [Indexed: 01/10/2023] Open
Abstract
BACKGROUND Measurement error in self-reported dietary intakes is known to bias the association between dietary intake and a health outcome of interest such as risk of a disease. The association can be distorted further by mismeasured confounders, leading to invalid results and conclusions. It is, however, difficult to adjust for the bias in the association when there is no internal validation data. METHODS We proposed a method to adjust for the bias in the diet-disease association (hereafter, association), due to measurement error in dietary intake and a mismeasured confounder, when there is no internal validation data. The method combines prior information on the validity of the self-report instrument with the observed data to adjust for the bias in the association. We compared the proposed method with the method that ignores the confounder effect, and with the method that ignores measurement errors completely. We assessed the sensitivity of the estimates to various magnitudes of measurement error, error correlations and uncertainty in the literature-reported validation data. We applied the methods to fruits and vegetables (FV) intakes, cigarette smoking (confounder) and all-cause mortality data from the European Prospective Investigation into Cancer and Nutrition study. RESULTS Using the proposed method resulted in about four times increase in the strength of association between FV intake and mortality. For weakly correlated errors, measurement error in the confounder minimally affected the hazard ratio estimate for FV intake. The effect was more pronounced for strong error correlations. CONCLUSIONS The proposed method permits sensitivity analysis on measurement error structures and accounts for uncertainties in the reported validity coefficients. The method is useful in assessing the direction and quantifying the magnitude of bias in the association due to measurement errors in the confounders.
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Affiliation(s)
- George O. Agogo
- Biometris, Wageningen University and Research Centre, Wageningen, The Netherlands
- Department of Internal Medicine, Yale University, New Haven, USA
| | - Hilko van der Voet
- Biometris, Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Pieter van ’t Veer
- Department of Human Nutrition, Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Pietro Ferrari
- Nutritional Epidemiology Group, International Agency for Research on Cancer, Lyon, France
| | - David C. Muller
- Genetic Epidemiology Group, International Agency for Research on Cancer, Lyon, France
| | | | - Christina Bamia
- Department of Hygiene, Epidemiology and Medical Statistics, University of Athens Medical School, Athens, Greece
| | - Tonje Braaten
- Department of Community Medicine, University of Tromsø, N-9037 Tromsø, Norway
| | - Sven Knüppel
- Department of Epidemiology, German Institute of Human Nutrition Potsdam-Rehbrücke, Nuthetal, Germany
| | | | - Fred A. van Eeuwijk
- Biometris, Wageningen University and Research Centre, Wageningen, The Netherlands
| | - Hendriek C. Boshuizen
- Department of Statistics, mathematical modelling and data logistics, National Institute for Public Health and the Environment (RIVM), Bilthoven, The Netherlands
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Abstract
To estimate a time series model for multiple individuals, a multilevel model may be used. In this paper we compare two estimation methods for the autocorrelation in Multilevel AR(1) models, namely Maximum Likelihood Estimation (MLE) and Bayesian Markov Chain Monte Carlo. Furthermore, we examine the difference between modeling fixed and random individual parameters. To this end, we perform a simulation study with a fully crossed design, in which we vary the length of the time series (10 or 25), the number of individuals per sample (10 or 25), the mean of the autocorrelation (-0.6 to 0.6 inclusive, in steps of 0.3) and the standard deviation of the autocorrelation (0.25 or 0.40). We found that the random estimators of the population autocorrelation show less bias and higher power, compared to the fixed estimators. As expected, the random estimators profit strongly from a higher number of individuals, while this effect is small for the fixed estimators. The fixed estimators profit slightly more from a higher number of time points than the random estimators. When possible, random estimation is preferred to fixed estimation. The difference between MLE and Bayesian estimation is nearly negligible. The Bayesian estimation shows a smaller bias, but MLE shows a smaller variability (i.e., standard deviation of the parameter estimates). Finally, better results are found for a higher number of individuals and time points, and for a lower individual variability of the autocorrelation. The effect of the size of the autocorrelation differs between outcome measures.
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Affiliation(s)
- Tanja Krone
- Department of Psychometrics and Statistics, Heymans Institute, University of Groningen Groningen, Netherlands
| | - Casper J Albers
- Department of Psychometrics and Statistics, Heymans Institute, University of Groningen Groningen, Netherlands
| | - Marieke E Timmerman
- Department of Psychometrics and Statistics, Heymans Institute, University of Groningen Groningen, Netherlands
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12
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Abstract
Comparative genomic sequencing is a major surveillance tool in the Polio Laboratory Network. Due to the rapid evolution of polioviruses (~1 % per year), pathways of virus transmission can be reconstructed from the pathways of genomic evolution. Here, we describe three main phylogenetic methods; estimation of genetic distances, reconstruction of a maximum-likelihood (ML) tree, and estimation of substitution rates using Bayesian Markov chain Monte Carlo (MCMC). The data set used consists of complete capsid sequences from a survey of poliovirus sequences available in GenBank.
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Affiliation(s)
- Jaume Jorba
- Polio and Picornavirus Laboratory Branch, Division of Viral Diseases, National Center for Immunization and Respiratory Disease, Centers for Disease Control and Prevention, 1600 Clifton Rd., NE MS G-10, Atlanta, GA, 30333, USA.
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13
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Abstract
Various estimators of the autoregressive model exist. We compare their performance in estimating the autocorrelation in short time series. In Study 1, under correct model specification, we compare the frequentist r1 estimator, C-statistic, ordinary least squares estimator (OLS) and maximum likelihood estimator (MLE), and a Bayesian method, considering flat (Bf) and symmetrized reference (Bsr) priors. In a completely crossed experimental design we vary lengths of time series (i.e., T = 10, 25, 40, 50 and 100) and autocorrelation (from −0.90 to 0.90 with steps of 0.10). The results show a lowest bias for the Bsr, and a lowest variability for r1. The power in different conditions is highest for Bsr and OLS. For T = 10, the absolute performance of all measurements is poor, as expected. In Study 2, we study robustness of the methods through misspecification by generating the data according to an ARMA(1,1) model, but still analysing the data with an AR(1) model. We use the two methods with the lowest bias for this study, i.e., Bsr and MLE. The bias gets larger when the non-modelled moving average parameter becomes larger. Both the variability and power show dependency on the non-modelled parameter. The differences between the two estimation methods are negligible for all measurements.
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Affiliation(s)
- Tanja Krone
- Heymans Institute for Psychological Research, Psychometrics and Statistics, Grote Kruisstraat 2/1, 9712TS Groningen, The Netherlands
| | - Casper J Albers
- Heymans Institute for Psychological Research, Psychometrics and Statistics, Grote Kruisstraat 2/1, 9712TS Groningen, The Netherlands
| | - Marieke E Timmerman
- Heymans Institute for Psychological Research, Psychometrics and Statistics, Grote Kruisstraat 2/1, 9712TS Groningen, The Netherlands
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14
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Feng D, Cortese G, Baumgartner R. A comparison of confidence/credible interval methods for the area under the ROC curve for continuous diagnostic tests with small sample size. Stat Methods Med Res 2015; 26:2603-2621. [PMID: 26323286 DOI: 10.1177/0962280215602040] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The receiver operating characteristic (ROC) curve is frequently used as a measure of accuracy of continuous markers in diagnostic tests. The area under the ROC curve (AUC) is arguably the most widely used summary index for the ROC curve. Although the small sample size scenario is common in medical tests, a comprehensive study of small sample size properties of various methods for the construction of the confidence/credible interval (CI) for the AUC has been by and large missing in the literature. In this paper, we describe and compare 29 non-parametric and parametric methods for the construction of the CI for the AUC when the number of available observations is small. The methods considered include not only those that have been widely adopted, but also those that have been less frequently mentioned or, to our knowledge, never applied to the AUC context. To compare different methods, we carried out a simulation study with data generated from binormal models with equal and unequal variances and from exponential models with various parameters and with equal and unequal small sample sizes. We found that the larger the true AUC value and the smaller the sample size, the larger the discrepancy among the results of different approaches. When the model is correctly specified, the parametric approaches tend to outperform the non-parametric ones. Moreover, in the non-parametric domain, we found that a method based on the Mann-Whitney statistic is in general superior to the others. We further elucidate potential issues and provide possible solutions to along with general guidance on the CI construction for the AUC when the sample size is small. Finally, we illustrate the utility of different methods through real life examples.
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Affiliation(s)
- Dai Feng
- 1 Biometrics Research, Merck Research Lab, NJ, USA
| | - Giuliana Cortese
- 2 Department of Statistical Sciences, University of Padova, Italy
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15
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Abe H, Mine J, Parchariyanon S, Takemae N, Boonpornprasert P, Ubonyaem N, Patcharasinghawut P, Nuansrichay B, Tanikawa T, Tsunekuni R, Saito T. Co-infection of influenza A viruses of swine contributes to effective shuffling of gene segments in a naturally reared pig. Virology 2015; 484:203-212. [PMID: 26115167 DOI: 10.1016/j.virol.2015.06.002] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Revised: 06/01/2015] [Accepted: 06/02/2015] [Indexed: 11/26/2022]
Abstract
Following the 2009 H1N1 pandemic, surveillance activities have been accelerated globally to monitor the emergence of novel reassortant viruses. However, the mechanism by which influenza A viruses of swine (IAV-S) acquire novel gene constellations through reassortment events in natural settings remains poorly understood. To explore the mechanism, we collected 785 nasal swabs from pigs in a farm in Thailand from 2011 to 2014. H3N2, H3N1, H1N1 and H1N2 IAVs-S were isolated from a single co-infected sample by plaque purification and showed a high degree of diversity of the genome. In particular, the H1N1 isolates, possessing a novel gene constellation previously unreported in Thailand, exhibited greater variation in internal genes than H3N2 IAVs-S. A pair of isolates, designated H3N2-B and H1N1-D, was determined to have been initially introduced to the farm. These results demonstrate that numerous IAVs-S with various gene constellations can be created in a single co-infected pig via reassortment.
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Affiliation(s)
- Haruka Abe
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Junki Mine
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Sujira Parchariyanon
- National Institute of Animal Health, Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Nobuhiro Takemae
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | | | - Namfon Ubonyaem
- National Institute of Animal Health, Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | | | - Bandit Nuansrichay
- National Institute of Animal Health, Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Taichiro Tanikawa
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Ryota Tsunekuni
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand
| | - Takehiko Saito
- Influenza and Prion Disease Research Center, National Institute of Animal Health, National Agriculture and Food Research Organization (NARO), Tsukuba 305-0856, Ibaraki, Japan; Thailand-Japan Zoonotic Diseases Collaboration Center (ZDCC), Kasetklang, Chatuchak, Bangkok 10900, Thailand.
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16
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Feng D, Baumgartner R, Svetnik V. A Bayesian estimate of the concordance correlation coefficient with skewed data. Pharm Stat 2015; 14:350-8. [PMID: 26033433 DOI: 10.1002/pst.1692] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2014] [Revised: 03/16/2015] [Accepted: 05/04/2015] [Indexed: 11/11/2022]
Abstract
Concordance correlation coefficient (CCC) is one of the most popular scaled indices used to evaluate agreement. Most commonly, it is used under the assumption that data is normally distributed. This assumption, however, does not apply to skewed data sets. While methods for the estimation of the CCC of skewed data sets have been introduced and studied, the Bayesian approach and its comparison with the previous methods has been lacking. In this study, we propose a Bayesian method for the estimation of the CCC of skewed data sets and compare it with the best method previously investigated. The proposed method has certain advantages. It tends to outperform the best method studied before when the variation of the data is mainly from the random subject effect instead of error. Furthermore, it allows for greater flexibility in application by enabling incorporation of missing data, confounding covariates, and replications, which was not considered previously. The superiority of this new approach is demonstrated using simulation as well as real-life biomarker data sets used in an electroencephalography clinical study. The implementation of the Bayesian method is accessible through the Comprehensive R Archive Network.
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Affiliation(s)
- Dai Feng
- Merck & Co., Inc., Rahway, NJ, USA
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