Evaluation using latent class models of the diagnostic performances of three ELISA tests commercialized for the serological diagnosis of <i>Coxiella burnetii</i> infection in domestic ruminants

International audienceELISA methods are the diagnostic tools recommended for the serological diagnosis of Coxiella burnetii infection in ruminants but their respective diagnostic performances are difficult to assess because of the absence of a gold standard. This study focused on three commercial ELISA tests with the following objectives (1) assess their sensitivity and specificity in sheep, goats and cattle, (2) assess the between-and within-herd seroprevalence distribution in these species, accounting for diagnostic errors, and (3) estimate optimal sample sizes considering sensitivity and specificity at herd level. We comparatively tested 1413 cattle, 1474 goat and 1432 sheep serum samples collected in France. We analyzed the cross-classified test results with a hierarchical zero-inflated beta-binomial latent class model considering each herd as a population and conditional dependence as a fixed effect. Potential biases and coverage probabilities of the model were assessed by simulation. Conditional dependence for truly seropositive animals was high in all species for two of the three ELISA methods. Specificity estimates were high, ranging from 94.8% [92.1; 97.8] to 99.2% [98.5; 99.7], whereas sensitivity estimates were generally low, ranging from 39.3 [30.7; 47.0] to 90.5% [83.3; 93.8]. Betweenand within-herd seroprevalence estimates varied greatly among geographic areas and herds. Overall, goats showed higher within-herd seroprevalence levels than sheep and cattle. The optimal sample size maximizing both herd sensitivity and herd specificity varied from 3 to at least 20 animals depending on the test and ruminant species. This study provides better interpretation of three widely used commercial ELISA tests and will make it possible to optimize their implementation in future studies. The methodology developed may likewise be applied to other human or animal diseases

DMTs and Covid-19 severity in MS: a pooled analysis from Italy and France

We evaluated the effect of DMTs on Covid-19 severity in patients with MS, with a pooled-analysis of two large cohorts from Italy and France. The association of baseline characteristics and DMTs with Covid-19 severity was assessed by multivariate ordinal-logistic models and pooled by a fixed-effect meta-analysis. 1066 patients with MS from Italy and 721 from France were included. In the multivariate model, anti-CD20 therapies were significantly associated (OR&nbsp;=&nbsp;2.05, 95%CI&nbsp;=&nbsp;1.39–3.02, p&nbsp;&lt;&nbsp;0.001) with Covid-19 severity, whereas interferon indicated a decreased risk (OR&nbsp;=&nbsp;0.42, 95%CI&nbsp;=&nbsp;0.18–0.99, p&nbsp;=&nbsp;0.047). This pooled-analysis confirms an increased risk of severe Covid-19 in patients on anti-CD20 therapies and supports the protective role of interferon

Phenotypic and functional analysis of osteoclasts and their precursors in cystic fibrosis-related bone disease

L’augmentation de l’espérance de vie des patients atteints par la mucoviscidose (CF, Cystic Fibrosis) est associée à des complications extra-pulmonaires dont la prévalence augmente avec l’âge, comme c’est le cas pour la maladie osseuse ou le diabète, représentant une véritable problématique pour la qualité de vie des patients CF. Le déficit osseux lié à la mucoviscidose reste encore incomplètement caractérisé et la compréhension de l’impact du défaut de fonction du canal CFTR (Cystic Fibrosis Transmembrane conductance Regulator) sur la physiologie osseuse est indispensable pour proposer de nouvelles stratégies thérapeutiques. La mutation la plus fréquente de CFTR (F508del) dans les ostéoblastes est associée à un ratio RANK-L/OPG élevé susceptible de stimuler l’ostéoclastogenèse. L’objectif de ce travail était d’étudier l’impact du défaut d’activité de CFTR sur les précurseurs ostéoclastiques et leur différenciation ainsi que l’activité fonctionnelle des ostéoclastes CF. Nous avons pu mettre en évidence qu’il existe une surexpression des récepteurs RANK et M-CSF à la surface des précurseurs ostéoclastiques issus de patients porteurs de la mutation G551D de CFTR. Par ailleurs, nous avons démontré que le phénotype ostéoclastique est fortement impacté par la mutation F508del, ainsi que la voie de la S1P, médiateur prépondérant dans la circulation des précurseurs ostéoclastiques entre les compartiments sanguins et osseux. L’ensemble de ces données et la mise en évidence d’un profil résorptif perturbé des ostéoclastes lorsque l’activité de CFTR est déficiente, suggèrent qu’il existe une dérégulation de la résorption, et plus largement du remodelage osseux chez les patients CF.The increasing life expectancy of patients with cystic fibrosis (CF) is associated with extra-pulmonary complications which prevalence increases with age, such as bone disease or diabetes, that impact the quality of life of CF patients. The bone deficit related to cystic fibrosis is still incompletely characterized and the understanding of the impact of CFTR (Cystic Fibrosis Transmembrane conductance Regulator) defect on bone physiology is essential to propose new therapeutic strategies. The most common mutation of CFTR, (F508del) in osteoblasts is associated with a high RANK-L/OPG ratio that may stimulate osteoclastogenesis. The aim of this work was to study the impact of CFTR defective activity on osteoclast precursors and their differentiation as well as the functional activity of CF osteoclasts. We have demonstrated that there is an overexpression of the RANK and M-CSF receptors on the surface of osteoclastic precursors derived from patients carrying the CFTR G551D mutation. Furthermore, we have revealed that the osteoclasts phenotype is strongly impacted by the F508del mutation as well as the S1P pathway, a prominent mediator for the circulation of osteoclastic precursors between blood and bone compartments. All of these data and the demonstration of a disturbed resorptive osteoclasts profile when CFTR activity is deficient suggest that there is a dysregulation of resorption and more widely of bone remodeling in CF patients

Evaluation de méthodes diagnostiques en l’absence de gold standard sur la base de variables binaires et continues : intérêt de l'approche bayésienne

National audienc

Evaluation de méthodes diagnostiques en l’absence de gold standard sur la base de variables binaires et continues : intérêt de l'approche bayésienne

National audienc

Interpretation of the results of Q fever ELISA tests in domestic ruminants : a user-friendly Shiny appli-cation based on latent class models in a Bayesian framework

International audienc

Interpretation of the results of ELISA tests commercialized for the serological diagnosis of Coxiella burnetii infection in domestic ruminants: a user-friendly Shiny application based on latent class models in a Bayesian framework

International audienceQ fever is a worldwide zoonotic disease, due to the bacterium Coxiella burnetii, responsible for reproductive disorders, such as abortion in domestic ruminants. Although direct detection of C. burnetii by quantitative PCR is primarily recommended for the direct diagnosis of Q fever in abortive contexts and identification of bacterial shedding, serological approaches aiming at detecting antibodies specific for C. burnetii are also useful at both the individual and herd levels. At the individual level, ELISA tests may be used to identify animals that were previously infected (with or without clinical signs and shedding) and may still be latently infected (carriers with or without shedding). At the herd level, ELISA tests may be used to reveal a past or recent exposure to C. burnetii within a considered farm, a key tool for a rapid screening (prevalence, current evolutive circulation). Recent investigations about the diagnostic accuracy of the three ELISA tests currently commercialized for their use in domestic ruminants showed that these tests are moderately sensitive (sensitivity values ranged between 40% and 94%) and that their specificities are inferior to 100% (specificity values ranged between 95% and 99%). As a consequence, the diagnostic uncertainty should be considered to limit potential misinterpretations of the individual or herd serological status.ObjectivesThe objectives of this study were (1) to build a methodological framework allowing calculating predictive values of Q fever ELISA tests at both the individual and the herd levels and (2) to provide a user-friendly application that could be easily used by veterinarians to interpret the results of a serological sample plan applied to a ruminant herd. Materials and methodsWe developed an advanced computing method based on latent class modeling, implemented using JAGS and R to calculate predictive values corresponding to the results obtained with any of the three commercialized ELISA tests, at both the individual and the herd levels. This method was integrated within an open source web application, using Shiny, to favor its accessibility to all the potential users of these ELISA tests (e.g., veterinarians, veterinary diagnostic laboratories, research laboratories). After completing the characteristics of the herd (species, herdsize, type of production) and the Q fever epidemiological context (if known), the users obtain the probability of true seropositivity of the tested herd and animals given the ELISA test results. The operation of this application is illustrated on a true clinical case where a Charolais bull originating from an apparently ‘free of infection’ herd was tested positive for Q fever by one ELISA test at introduction. To confirm or infirm these test results, additional animals in the herd of origin were tested with the same ELISA, considering firstly five heifers raised with the bull and secondly all males and females more than two-year-old (N=149). Probabilities of true seropositivity of the bull and its originating herd were calculated thanks to the developed application.ResultsThe five other animals initially tested animals that were raised with the seropositive bull were negative to the ELISA test, which corresponds, in regard to the test used and to the herd characteristics to a probability of the bull’s true seropositivity estimated at 0.85 with a 95% credibility interval (CI) of [0.14; 0.98].Among the animals older than two years present in the herd, 5 out of the 149 tested animals tested positive which corresponds for each positive animal to a probability of true seropositivity estimated at 0 with a 95% CI of [0 ; 0.65]. At the herd level, the probability that the proportion of seropositive animals was above 0 was estimated at 0 with a 95% CI of [0 ; 0.58]; and if the herd was truly seropositive, the proportion of truly seropositive animals in the herd was assessed to 0.06 with a 95% CI of [0.02; 0.12].ConclusionThis application assists veterinarians in a proper interpretation of the results of Q fever ELISA tests according to the sampling size and to available epidemiological and herd information. Veterinarians can therefore easily take advantage of a complex statistical model in a Bayesian framework to support their daily work related to Q fever risk analysis in ruminants. In the absence of a perfect reference test, this application could also be useful for local and reference laboratories for the confirmatory diagnosis of an ELISA test result

Interpretation of the results of Q fever ELISA tests in domestic ruminants : a user-friendly Shiny appli-cation based on latent class models in a Bayesian framework

International audienc

Cationic antimicrobial peptides and periodontal physiopathology: A systematic review

International audienc

Coxiella burnetii within- and between-herd true seroprevalence assessment in domestic ruminants in France accounting for diagnostic uncertainty with latent class

International audienc