Objective Bayes testing of Poisson versus inflated Poisson models

The Poisson distribution is often used as a standard model for count data. Quite often, however, such data sets are not well fit by a Poisson model because they have more zeros than are compatible with this model. For these situations, a zero-inflated Poisson (ZIP) distribution is often proposed. This article addresses testing a Poisson versus a ZIP model, using Bayesian methodology based on suitable objective priors. Specific choices of objective priors are justified and their properties investigated. The methodology is extended to include covariates in regression models. Several applications are given.Comment: Published in at http://dx.doi.org/10.1214/074921708000000093 the IMS Collections (http://www.imstat.org/publications/imscollections.htm) by the Institute of Mathematical Statistics (http://www.imstat.org

Occurrence of pesticide residues in Spanish honey measured by QuEChERS method followed by liquid and gas chromatography–Tandem mass spectrometry

In the current study, the QuEChERS extraction method with slight modifications, followed by liquid and gas chromatography–tandem mass spectrometry, was applied for the determination of 399 pesticide residues in 91 raw honey samples from northeastern Spain. The quality control proce-dure established in Document No. SANTE/12682/2019 was successfully followed: the responses in reagent blank and blank honey samples were below 30% of the reporting limit (0.01 mg kg-1) for all analysed compounds, the correlation coefficients (R2) were higher than 0.99 in most calibration curves, the deviation of back-calculated concentration from the true concentration was below ±20% (using the standard of 50 µg L-1 concentration), and the recoveries of spiked samples on matrix were within the range of 70–120% for almost all analytes. Only chlorfenvinphos (2–7.8 ng/g) and coumaphos (8.8–37 ng/g) were detected in 13 samples, and neither were observed to exceed their maximum residue limits (MRLs). Dietary risk assessment for pesticide residues in honey above their lowest calibrated level (LCL) was performed, and two different age groups, adults and infants, were considered as populations at risk. The contribution of honey lay far below the acceptable daily intake (ADI) for both pesticide residues. Therefore, according to our results, honey is unlikely to pose concerns for consumer health in terms of its contribution to dietary long-term exposure. However, to maintain the level of compliance, pesticide residues in honey should be continuously monitored. © 2021 by the authors. Licensee MDPI, Basel, Switzerland

Toxoplasma gondii in Spanish commercial dry-cured meat products

Toxoplasmosis is an infection caused by Toxoplasma gondii, the transmission of which has usually been attributed to ingestion of undercooked or raw meat. Epidemiological studies also mention cured meat products as a potential risk factor for acquiring toxoplasmosis. With the aim of contributing to the risk assessment process, 552 samples of commercial dry-cured hams/shoulders and dry-cured sausages of different trademarks from different localities in Spain were randomly purchased for analysis. These were, specifically, 311 dry-cured hams/shoulders and 241 dry-cured sausages (76 samples of chorizo, 75 samples of fuet/longaniza, and 90 samples of salchichón). Additionally, data featured on labels of each meat product were gathered with the purpose of studying the influence of curing time and salt content, among other parameters, on the viability of Toxoplasma. Real-time polymerase chain reaction technique (qPCR) was performed to detect T. gondii DNA in the samples, and infectivity was determined by mouse bioassay of positive qPCR samples. The presence of T. gondii was detected in 57 samples (10.3%), with a parasite load between 28.05 and 35.66 Ct. Bioassay test showed that 47 out of the 57 meat products in which the parasite has been detected produced mice seropositive response (IFA), which represents 8.5 of the total number of samples analyzed. Of those samples, DNA of Toxoplasma gondii in mice brain was detected in 6 meat products, indicating its viability (1.1%). Ct values obtained by qPCR in the brains of seropositive mice ranged from 33.10 to 36.04. According to product type, the parasite was viable in 3 dry-cured ham/shoulder samples and in 3 salchichón samples. Statistical analysis showed that none of the variables under consideration detailed on the meat product labels had a significant influence on the viability of the parasite. In conclusion, we found a low prevalence of the infective forms of Toxoplasma gondii in cured meat products, although the risk for consumers cannot be completely excluded. However, scientific monitoring of commercial meat products continues to be necessary in order to provide data for risk assessment of Toxoplasma gondii through the meat industry's Hazard Analysis and Critical Control Point (HACCP-based self-control system). In order to ensure that consumers can make a safe choice among these ready-to-eat products, it is important for food labels to include information on those parameters which are relevant for the survival of the parasite, such as curing times, or freezing treatment of meat used as an ingredient

Comparative evaluation of impedanciometry combined with chromogenic agars or RNA hybridization and real-time PCR methods for the detection of L. monocytogenes in dry-cured ham

Listeria monocytogenes is an important foodborne pathogen of particular relevance in “Ready To Eat” products. Food producers require rapid methods to detect L. monocytogenes, since the reference method (ISO 11290-1) is laborious, lengthy and costly. The aim of this study was to evaluate three alternative methods to detect L. monocytogenes in dry-cured ham following the ISO 16140-2:2016 standard: (A) impedance measurement followed by plating onto chromogenic agars; (B) impedance measurement followed by RNA hybridization, and (C) real-time PCR. Inclusivity and exclusivity were evaluated. The limits of detection 50 (LOD50) and the relative limits of detection (RLOD) were obtained by analysing dry-cured ham samples inoculated with L. monocytogenes at three different levels of contamination. The sensitivity study of alternative methods, as well as the relative specificity (SP), sensitivity (SE), and Kappa Cohen''s index were calculated analysing 93 samples of sliced dry-cured ham. The inclusivity and exclusivity tests of three methods showed no interference in pathogen detection. LOD50 were very low for the three methods evaluated (<1 cfu/25 g dry-cured ham). The RLOD values of the three alternative methods were below the acceptability limit established by ISO 16140. For methods A and C, good results were obtained in the sensitivity study, as well as in the SP and SE. However, method B showed poorer results in the sensitivity study, along with lower results for SP (99.7%) and SE (79.6%), due to the occurrence of false positives and negatives in samples with presence of other Listeria spp. Methods A and C were considered to be a thoroughly appropriate control tool for use in the meat industry to improve the detection of L. monocytogenes

Tissue iron quantification in chronic liver diseases using MRI shows a relationship between iron accumulation in liver, spleen, and bone marrow

Aim: To investigate iron loading within the liver, pancreas, spleen, and bone marrow using magnetic resonance imaging (MRI) transverse relaxation rate (R2*), in patients with diffuse liver diseases; to evaluate the relationships between iron accumulation in these tissue compartments; and to assess the association between tissue iron overload and the pattern of hepatic cellular iron distribution (hepatocytes versus Kupffer cells). Material and methods: Fifty-six patients with diffuse liver diseases had MRI-derived R2* values, using a multi-echo chemical-shift encoded MRI sequence, of the liver, pancreas, spleen, and vertebral bone marrow. All patients had liver biopsy samples scored for hepatic iron grading (0–4) and iron cellular distribution (within hepatocytes only or within both hepatocytes and Kupffer cells). Results: Liver R2* increased with histological iron grade (RS=0.58, p<0.001) and correlated with spleen (RS=0.71, p<0.001) and bone marrow R2* (RS=0.66, p<0.001), but not with pancreatic R2* (RS=0.22, p=0.096). Splenic and bone marrow R2* values were also correlated (RS=0.72, p<0.001). Patients with iron inside Kupffer cells had the highest R2* in liver, spleen and bone marrow. Conclusions: Patients with chronic diffuse liver diseases have concomitant hepatic, splenic, and bone marrow iron loading. The highest hepatic iron scores and iron inside Kupffer cells were associated with the highest splenic and bone marrow deposits, suggesting systemic iron accumulation in the mononuclear phagocytic system.The present study was supported by the Teaching and Research Department of Centro Hospitalar do Porto with a research grant number DEFI:309/12(213-DEFI/251-CES). The funder had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. L.M.B. and A.A.B. are co-founders of QUIBIM SME

Optimizing the management of hereditary haemochromatosis: the value of MRI R2* quantification to predict and monitor body iron stores

This study was supported by a research Grant from the Teaching and Research Department of Centro Hospitalar do Porto (grant number DEFI:309/12(213-DEFI/251-CES). The funder had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript

ESR Statement on the Validation of Imaging Biomarkers

Medical imaging capable of generating imaging biomarkers, specifically radiology and nuclear medicine image acquisition and analysis processes, differs from frequently used comparators like blood or urine biomarkers. This difference arises from the sample acquisition methodology. While different analysis methodologies and equipment provide slightly different results in any analytical domain, unlike blood or urine analysis where the samples are obtained by simple extraction or excretion, in radiology the acquisition of the sample is heterogeneous by design, since complex equipment from different vendors is used. Therefore, with this additional degree of freedom in medical imaging, there is still risk of persistent heterogeneity of image quality through time, due to different technological implementations across vendors and protocols used in different centres. Quantitative imaging biomarkers have yet to demonstrate an impact on clinical practice due to this lack of comprehensive standardisation in terms of technical aspects of image acquisition, analysis algorithms, processes and clinical validation. The aim is establishing a standard methodology based on metrology for the validation of image acquisition and analysis methods used in the extraction of biomarkers and radiomics data. The appropriate implementation of the guidelines herein proposed by radiology departments, research institutes and industry will allow for a significant reduction in inter-vendor & inter-centre variability in imaging biomarkers and determine the measurement error obtained, enabling them to be used in imaging-based criteria for diagnosis, prognosis or treatment response, ultimately improving clinical workflows and patient care. The validation of developed analytical methods must be based on a technical performance validation and clinical validation