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OBJECTIVE: Maternal history of inflammatory conditions has been linked to offspring developmental and behavioural outcomes. This phenomenon may be explained by the maternal immune activation (MIA) hypothesis, which posits that dysregulation of the gestational immune environment affects foetal neurodevelopment. The timing of inflammation is critical. We aimed to understand maternal asthma symptoms during pregnancy, in contrast with paternal asthma symptoms during the same period, on child behaviour problems and executive function in a population-based cohort. METHODS: Data were obtained from 844 families from the Growing Up in Singapore Towards healthy Outcomes (GUSTO) birth cohort. Parent asthma symptoms during the prenatal period were reported. Asthma symptoms in children were reported longitudinally from two to five years old, while behavioural problems and executive functioning were obtained at seven years old. Parent and child measures were compared between mothers with and without prenatal asthma symptoms. Generalized linear and Bayesian phenomics models were used to determine the relation between parent or child asthma symptoms and child outcomes. RESULTS: Children of mothers with prenatal asthma symptoms had greater behavioural and executive problems than controls (Cohen's d: 0.43-0.75; all p < 0.05). This association remained after adjustments for emerging asthma symptoms during the preschool years and fathers' asthma symptoms during the prenatal period. After adjusting for dependence between child outcomes, the Bayesian phenomics model showed that maternal prenatal asthma symptoms were associated with child internalising symptoms and higher-order executive function, while child asthma symptoms were associated with executive function skills. Paternal asthma symptoms during the prenatal period were not associated with child outcomes. CONCLUSIONS: Associations between child outcomes and maternal but not paternal asthma symptoms during the prenatal period suggests a role for MIA. These findings need to be validated in larger samples, and further research may identify behavioural and cognitive profiles of children with exposure to MIA.
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Asma , Efeitos Tardios da Exposição Pré-Natal , Criança , Masculino , Pré-Escolar , Feminino , Gravidez , Humanos , Função Executiva , Teorema de Bayes , Fenômica , Mães/psicologia , Comportamento InfantilRESUMO
Time-to-event data are often recorded on a discrete scale with multiple, competing risks as potential causes for the event. In this context, application of continuous survival analysis methods with a single risk suffers from biased estimation. Therefore, we propose the multivariate Bernoulli detector for competing risks with discrete times involving a multivariate change point model on the cause-specific baseline hazards. Through the prior on the number of change points and their location, we impose dependence between change points across risks, as well as allowing for data-driven learning of their number. Then, conditionally on these change points, a multivariate Bernoulli prior is used to infer which risks are involved. Focus of posterior inference is cause-specific hazard rates and dependence across risks. Such dependence is often present due to subject-specific changes across time that affect all risks. Full posterior inference is performed through a tailored local-global Markov chain Monte Carlo (MCMC) algorithm, which exploits a data augmentation trick and MCMC updates from nonconjugate Bayesian nonparametric methods. We illustrate our model in simulations and on ICU data, comparing its performance with existing approaches.
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Algoritmos , Teorema de Bayes , Simulação por Computador , Cadeias de Markov , Método de Monte Carlo , Humanos , Análise de Sobrevida , Modelos Estatísticos , Análise Multivariada , Biometria/métodosRESUMO
The prevalence of chronic non-communicable diseases such as obesity has noticeably increased in the last decade. The study of these diseases in early life is of paramount importance in determining their course in adult life and in supporting clinical interventions. Recently, attention has been drawn to approaches that study the alteration of metabolic pathways in obese children. In this work, we propose a novel joint modeling approach for the analysis of growth biomarkers and metabolite associations, to unveil metabolic pathways related to childhood obesity. Within a Bayesian framework, we flexibly model the temporal evolution of growth trajectories and metabolic associations through the specification of a joint nonparametric random effect distribution, with the main goal of clustering subjects, thus identifying risk sub-groups. Growth profiles as well as patterns of metabolic associations determine the clustering structure. Inclusion of risk factors is straightforward through the specification of a regression term. We demonstrate the proposed approach on data from the Growing Up in Singapore Towards healthy Outcomes cohort study, based in Singapore. Posterior inference is obtained via a tailored MCMC algorithm, involving a nonparametric prior with mixed support. Our analysis has identified potential key pathways in obese children that allow for the exploration of possible molecular mechanisms associated with childhood obesity.
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Obesidade Infantil , Adulto , Humanos , Criança , Obesidade Infantil/epidemiologia , Estudos de Coortes , Teorema de Bayes , Fatores de Risco , BiomarcadoresRESUMO
BACKGROUND: Owing to the evidence that as many as 30-40% of patients with vulvar lichen sclerosus (VLS) fail to report a remission of symptoms with first-line corticosteroid treatment (TCS), especially as what regards dyspareunia, we aimed to analyze patients' satisfaction following vulvar injection of autologous platelet-rich plasma (PRP). This is intended as an adjunctive treatment, to be used following TCS, and appears to promote tissue repair. It may also possibly have immunomodulatory proprieties. MATERIALS AND METHODS: Patients with VLS were considered eligible for this pilot study if, despite having been treated with a 3-month TCS regimen, they reported a persistence of symptoms. PRP was produced in a referral center using a manual method and a standardized protocol. Each patient received three treatments 4 to 6 weeks apart. RESULTS: A total of 50 patients with a median age of 53 years [IQR 38-59 years] were included in the study. 6 months after the last injection of PRP all patients were either satisfied or very satisfied with the treatment (100%; 95% CI 93-100%). Median NRS scores for itching, burning, dyspareunia and dysuria were significantly reduced (p < 0.05) and FSFI, HADS and SF-12 questionnaires revealed a significant improvement in sexual function, psychological wellbeing and quality of life (p < 0.05). The number of patients reporting the need for maintenance TCS treatment was reduced by 42% (p < 0.001) and an improvement in vulvar elasticity and color was reported in all patients. CONCLUSION: Following standard medical therapy, PRP may be effective not only in improving symptoms, but also in restoring function.
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Dispareunia , Satisfação do Paciente , Plasma Rico em Plaquetas , Líquen Escleroso Vulvar , Humanos , Feminino , Projetos Piloto , Líquen Escleroso Vulvar/terapia , Líquen Escleroso Vulvar/tratamento farmacológico , Pessoa de Meia-Idade , Adulto , Dispareunia/terapia , Dispareunia/etiologia , Resultado do Tratamento , InjeçõesRESUMO
BACKGROUND AND OBJECTIVES: COVID-19 convalescent plasma (CCP) has retained potency and clinical efficacy against SARS-CoV-2 and is currently of utmost value for seronegative immunocompromised patients. Since most of the effect is due to the vaccine boost of infection-elicited antibodies, there is a theoretical concern that the frequency of suitable donors is declining. MATERIALS AND METHODS: In this single-institution serosurvey, we screened 599 consecutive donors attending our area in two different seasons (300 in November 2022 and 299 in February 2023) using the Abbott Alinity® anti-Spike immunoglobulin G assay. RESULTS: More than 80% of random donors qualify according to the FDA criteria for high-titre CCP (>4350 AU/mL), with a stable trend. CONCLUSION: Despite reduced anti-Spike vaccine boost deployment in the general population, we have shown here that high-titre CCP units are easier than ever to procure. This finding also has implications for the derivation of standard immunoglobulins, which are finally approaching the potency of hyperimmune serum and could soon represent an alternative to CCP.
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COVID-19 , Vacinas Anticâncer , Humanos , Doadores de Sangue , COVID-19/terapia , Soroterapia para COVID-19 , SARS-CoV-2 , Itália , Imunoglobulina G , Anticorpos Antivirais/uso terapêutico , Imunização Passiva , Anticorpos NeutralizantesRESUMO
Several applications involving counts present a large proportion of zeros (excess-of-zeros data). A popular model for such data is the hurdle model, which explicitly models the probability of a zero count, while assuming a sampling distribution on the positive integers. We consider data from multiple count processes. In this context, it is of interest to study the patterns of counts and cluster the subjects accordingly. We introduce a novel Bayesian approach to cluster multiple, possibly related, zero-inflated processes. We propose a joint model for zero-inflated counts, specifying a hurdle model for each process with a shifted Negative Binomial sampling distribution. Conditionally on the model parameters, the different processes are assumed independent, leading to a substantial reduction in the number of parameters as compared with traditional multivariate approaches. The subject-specific probabilities of zero-inflation and the parameters of the sampling distribution are flexibly modelled via an enriched finite mixture with random number of components. This induces a two-level clustering of the subjects based on the zero/non-zero patterns (outer clustering) and on the sampling distribution (inner clustering). Posterior inference is performed through tailored Markov chain Monte Carlo schemes. We demonstrate the proposed approach on an application involving the use of the messaging service WhatsApp. This article is part of the theme issue 'Bayesian inference: challenges, perspectives, and prospects'.
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Mycobacterium avium ssp. paratuberculosis (MAP), causes Johne's disease (JD), or paratuberculosis, a chronic enteritis of ruminants, which in goats is characterized by ileal lesions. The work described here is a case-control association study using the Illumina Caprine SNP50 BeadChip to unravel the genes involved in susceptibility of goats to JD. Goats in herds with a high occurrence of Johne's disease were classified as healthy or infected based on the level of serum antibodies against MAP, and 331 animals were selected for the association study. Goats belonged to the Jonica (157) and Siriana breeds (174). Whole-genome association analysis identified one region suggestive of significance associated with an antibody response to MAP on chromosome 7 (p-value = 1.23 × 10-5 ). These results provide evidence for genetic loci involved in the antibody response to MAP in goats.
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Doenças dos Bovinos , Doenças das Cabras , Mycobacterium avium subsp. paratuberculosis , Paratuberculose , Animais , Bovinos , Paratuberculose/genética , Paratuberculose/epidemiologia , Paratuberculose/microbiologia , Cabras/genética , Estudo de Associação Genômica Ampla/veterinária , Mycobacterium avium/genética , Formação de Anticorpos/genética , Mycobacterium avium subsp. paratuberculosis/genética , Ensaio de Imunoadsorção Enzimática/veterinária , Doenças dos Bovinos/genética , Doenças das Cabras/genéticaRESUMO
PURPOSE: The main aim of this study was to investigate the long-term risk of disease recurrence in women treated for high-grade vaginal intraepithelial neoplasia (HG-VaIN). METHODS: We conducted a retrospective analysis on a cohort of 82 women diagnosed with HG-VaIN between 2010 and 2021 at the "Regional Referral Center for Prevention, Diagnosis and Treatment of HPV-related Genital Disorders", Fondazione IRCCS Ca' Granda Ospedale Maggiore Policlinico, Milan, Italy. All women underwent either ablative treatment (CO2 laser ablation or electrocoagulation) or cold-knife excision. RESULTS: In our series, the recurrence rate following treatment was 17%. The 5-year cumulative probability of recurrence was 30.4% and the median time to recurrence was 15.5 months. None of the patients progressed to invasive vaginal cancer during follow-up. A concomitant cervical or vulvar intraepithelial lesion was significatively associated with an increased risk of recurrence (p = 0.006). CONCLUSIONS: The results of our study suggest that women with HG-VaIN are at high risk of developing disease recurrence after treatment, especially patients with a concomitant cervical or vulvar intraepithelial lesion. In these women strict monitoring is mandatory to obtain an early identification of recurrence.
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Carcinoma in Situ , Neoplasias do Colo do Útero , Neoplasias Vaginais , Humanos , Feminino , Neoplasias Vaginais/cirurgia , Neoplasias Vaginais/diagnóstico , Estudos Retrospectivos , Vagina/patologia , Carcinoma in Situ/epidemiologia , Carcinoma in Situ/cirurgia , Itália/epidemiologia , Recidiva Local de Neoplasia/epidemiologia , Neoplasias do Colo do Útero/patologiaRESUMO
The efficacy of metformin in treating cancer has been extensively investigated since epidemiologic studies associated this anti-diabetic drug with a lower risk of cancer incidence. Since tumors are complex systems, in which cancer cells coexist and interact with several different types of non-malignant cells, it is not surprising that anti-cancer drugs affect not only cancer cells, but also the abundance and functions of cells of the tumor microenvironment. Recent years have seen a wide collection of reports showing how metformin, as well as other complex I inhibitors, may influence cancer progression by modulating the phenotype of non-transformed cells in a tumor. In this review, we particularly focus on the effect of metformin on angiogenesis, cancer-associated fibroblasts, tumor-associated macrophages and cancer immunosuppression.
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Antineoplásicos/farmacologia , Hipoglicemiantes/farmacologia , Metformina/farmacologia , Neoplasias/tratamento farmacológico , Microambiente Tumoral/efeitos dos fármacos , Animais , Fibroblastos/efeitos dos fármacos , Fibroblastos/patologia , Humanos , Macrófagos/efeitos dos fármacos , Macrófagos/patologia , Neoplasias/patologia , Neovascularização Patológica/tratamento farmacológico , Neovascularização Patológica/patologiaRESUMO
OBJECTIVE: This study aimed to evaluate the effectiveness of conservative treatment for cervical adenocarcinoma in situ (AIS). MATERIALS AND METHODS: This is a retrospective study on women with histologically confirmed AIS on cervical loop electrosurgical excision procedure specimen, treated conservatively between 2008 and 2020 in our center, Ospedale Maggiore Policlinico, Milan. The main outcome investigated was the risk of recurrence defined as a subsequent finding of recurrent AIS or invasive adenocarcinoma in a long-term follow-up. The disease-free survival curve was computed using the Kaplan-Meyer method. All patients underwent colposcopy with endocervical curettage and cytology every 6 months for the first 2 years after initial surgery and then annual cytology. RESULTS: Thirty women, aged 26 to 51 years, with histologically proven AIS on excisional specimen with negative margins, negative apex, and negative endocervical curettage were included. The median follow-up was 5.4 years. One woman had a recurrence of AIS after 8 years of follow-up and underwent total hysterectomy. No invasive cervical disease was detected during surveillance. CONCLUSIONS: Women with cervical AIS can be managed conservatively by an excisional procedure, provided that the margins are free and a close and long-term follow-up is guaranteed.
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Adenocarcinoma in Situ , Displasia do Colo do Útero , Neoplasias do Colo do Útero , Adenocarcinoma in Situ/cirurgia , Tratamento Conservador , Eletrocirurgia/métodos , Feminino , Humanos , Estudos Retrospectivos , Resultado do Tratamento , Neoplasias do Colo do Útero/patologia , Displasia do Colo do Útero/cirurgiaRESUMO
Heart failure (HF) is one of the main causes of morbidity, hospitalization, and death in the western world, and the economic burden associated with HF management is relevant and expected to increase in the future. We consider hospitalization data for HF in the most populated Italian Region, Lombardia. Data were extracted from the administrative data warehouse of the regional healthcare system. The main clinical outcome of interest is time to death and research focus is on investigating how recurrent hospitalizations affect the time to event. The main contribution of the article is to develop a joint model for gap times between consecutive rehospitalizations and survival time. The probability models for the gap times and for the survival outcome share a common patient specific frailty term. Using a flexible Dirichlet process model for %Bayesian nonparametric prior as the random-effects distribution accounts for patient heterogeneity in recurrent event trajectories. Moreover, the joint model allows for dependent censoring of gap times by death or administrative reasons and for the correlations between different gap times for the same individual. It is straightforward to include covariates in the survival and/or recurrence process through the specification of appropriate regression terms. The main advantages of the proposed methodology are wide applicability, ease of interpretation, and efficient computations. Posterior inference is implemented through Markov chain Monte Carlo methods.
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Insuficiência Cardíaca/mortalidade , Insuficiência Cardíaca/terapia , Hospitalização/estatística & dados numéricos , Modelos Teóricos , Humanos , RecidivaRESUMO
Statistical analysis of questionnaire data is often performed employing techniques from item-response theory. In this framework, it is possible to differentiate respondent profiles and characterize the questions (items) included in the questionnaire via interpretable parameters. These models are often crosssectional and aim at evaluating the performance of the respondents. The motivating application of this work is the analysis of psychometric questionnaires taken by a group of mothers at different time points and by their children at one later time point. The data are available through the GUSTO cohort study. To this end, we propose a Bayesian semiparametric model and extend the current literature by: (i) introducing temporal dependence among questionnaires taken at different time points; (ii) jointly modeling the responses to questionnaires taken from different, but related, groups of subjects (in our case mothers and children), introducing a further dependency structure and therefore sharing of information; (iii) allowing clustering of subjects based on their latent response profile. The proposed model is able to identify three main groups of mother/child pairs characterized by their response profiles. Furthermore, we report an interesting maternal reporting bias effect strongly affecting the clustering structure of the mother/child dyads.
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Mães , Teorema de Bayes , Criança , Estudos de Coortes , Feminino , Humanos , Psicometria , Inquéritos e QuestionáriosRESUMO
OBJECTIVES: The purpose of this cross-sectional study was to prepare a reliable and easy-to-use architectural classification for vulvar lichen sclerosus (VLS) aimed at defining the morphological patterns of this condition. MATERIALS AND METHODS: An expert panel composed by 7 physicians with expertise in clinical care of vulvar conditions outlined the architectural criteria for the definition of VLS severity (phimosis of the clitoris, involvement of the interlabial sulci, narrowing of the vulvar introitus), identifying 5 grades to build up a classification. Thirteen physicians with 2-30 years expertise in vulvar diseases (nonexpert group) were asked to evaluate 3-5 pictures from 137 patients. Each physician individually assigned a grade to each case, according to the previously mentioned criteria. Interrater reliability was analyzed by means of intraclass correlation coefficient (ICC). The reliability concerning the 2 classifications of each rater was analyzed by means of κ statistic. Intraobserver and interobserver reliability in vivo was analyzed by means of κ index. RESULTS: This study provides a new classification of VLS, based on defined anatomical criteria and graded into mutually exclusive progressive classes.The ICC analysis showed a substantial interrater reliability of the classification, ICC = 0.89 (0.87-0.91), both in the expert panel and in the nonexpert group (ICC = 0.92 and 0.87, respectively). An "almost perfect" intraobserver and interobserver reliability was achieved among physicians in vivo (κ = 0.93). CONCLUSIONS: Our classification showed a high reliability. It is easy to use, and it can be applied in clinical practice and eventually, in the evaluation of regenerative and cosmetic surgery.
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Líquen Escleroso Vulvar , Estudos Transversais , Feminino , Humanos , Masculino , Reprodutibilidade dos Testes , Líquen Escleroso Vulvar/diagnósticoRESUMO
BACKGROUND: Network meta-analysis (NMA) provides a powerful tool for the simultaneous evaluation of multiple treatments by combining evidence from different studies, allowing for direct and indirect comparisons between treatments. In recent years, NMA is becoming increasingly popular in the medical literature and underlying statistical methodologies are evolving both in the frequentist and Bayesian framework. Traditional NMA models are often based on the comparison of two treatment arms per study. These individual studies may measure outcomes at multiple time points that are not necessarily homogeneous across studies. METHODS: In this article we present a Bayesian model based on B-splines for the simultaneous analysis of outcomes across time points, that allows for indirect comparison of treatments across different longitudinal studies. RESULTS: We illustrate the proposed approach in simulations as well as on real data examples available in the literature and compare it with a model based on P-splines and one based on fractional polynomials, showing that our approach is flexible and overcomes the limitations of the latter. CONCLUSIONS: The proposed approach is computationally efficient and able to accommodate a large class of temporal treatment effect patterns, allowing for direct and indirect comparisons of widely varying shapes of longitudinal profiles.
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Algoritmos , Teorema de Bayes , Humanos , Estudos Longitudinais , Metanálise em RedeRESUMO
The bacterial deacetylase LpxC is a promising target for the development of antibiotics selectively combating Gram-negative bacteria. To improve the biological activity of the reported benzyloxyacetohydroxamic acid 9 ((S)-N-hydroxy-2-{2-hydroxy-1-[4-(phenylethynyl)phenyl]ethoxy}acetamide), its hydroxy group was replaced by a triazole ring. Therefore, in divergent syntheses, triazole derivatives exhibiting rigid and flexible lipophilic side chains, different configurations at their stereocenter, and various substitution patterns at the triazole ring were synthesized, tested for antibacterial and LpxC inhibitory activity, and structure-activity relationships were deduced based on docking and binding energy calculations.
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Amidoidrolases/antagonistas & inibidores , Antibacterianos/síntese química , Proteínas de Bactérias/antagonistas & inibidores , Inibidores Enzimáticos/síntese química , Ácidos Hidroxâmicos/síntese química , Triazóis/química , Antibacterianos/farmacologia , Reação de Cicloadição , Inibidores Enzimáticos/farmacologia , Bactérias Gram-Negativas/efeitos dos fármacos , Humanos , Ácidos Hidroxâmicos/farmacologia , Testes de Sensibilidade Microbiana , Simulação de Acoplamento Molecular , Estrutura Molecular , Estereoisomerismo , Relação Estrutura-AtividadeRESUMO
Many allosteric binding sites that modulate gamma aminobutyric acid (GABA) effects have been described in heteropentameric GABA type A (GABAA) receptors, among them sites for benzodiazepines, pyrazoloquinolinones and etomidate. Diazepam not only binds at the high affinity extracellular "canonical" site, but also at sites in the transmembrane domain. Many ligands of the benzodiazepine binding site interact also with homologous sites in the extracellular domain, among them the pyrazoloquinolinones that exert modulation at extracellular α+/ß- sites. Additional interaction of this chemotype with the sites for etomidate has also been described. We have recently described a new indole-based scaffold with pharmacophore features highly similar to pyrazoloquinolinones as a novel class of GABAA receptor modulators. Contrary to what the pharmacophore overlap suggests, the ligand presented here behaves very differently from the identically substituted pyrazoloquinolinone. Structural evidence demonstrates that small changes in pharmacophore features can induce radical changes in ligand binding properties. Analysis of published data reveals that many chemotypes display a strong tendency to interact promiscuously with binding sites in the transmembrane domain and others in the extracellular domain of the same receptor. Further structural investigations of this phenomenon should enable a more targeted path to less promiscuous ligands, potentially reducing side effect liabilities.
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Antagonistas de Receptores de GABA-A/química , Antagonistas de Receptores de GABA-A/farmacologia , Domínios Proteicos/efeitos dos fármacos , Receptores de GABA-A/metabolismo , Regulação Alostérica/efeitos dos fármacos , Animais , Benzodiazepinas/química , Benzodiazepinas/farmacologia , Sítios de Ligação/efeitos dos fármacos , Desenho de Fármacos , Humanos , Ligantes , Modelos Moleculares , Quinolonas/química , Quinolonas/farmacologia , Receptores de GABA-A/química , Ácido gama-Aminobutírico/metabolismoRESUMO
GABAA receptor modulators are structurally almost as diverse as their target protein. A plethora of heterocyclic scaffolds has been described as modulating this extremely important receptor family. Some made it into clinical trials and, even on the market, some were dismissed. This review focuses on the synthetic accessibility and potential for library synthesis of GABAA receptor modulators containing at least one heterocyclic scaffold, which were disclosed within the last 10 years.
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Agonistas de Receptores de GABA-A/síntese química , Antagonistas de Receptores de GABA-A/síntese química , Compostos Heterocíclicos/síntese química , Receptores de GABA-A/química , Bibliotecas de Moléculas Pequenas/síntese química , Regulação Alostérica , Animais , Ensaios Clínicos como Assunto , Agonistas de Receptores de GABA-A/farmacologia , Antagonistas de Receptores de GABA-A/farmacologia , Compostos Heterocíclicos/farmacologia , Humanos , Estrutura Molecular , Bibliotecas de Moléculas Pequenas/farmacologia , Relação Estrutura-AtividadeRESUMO
We propose a novel Bayesian nonparametric process prior for modeling a collection of random discrete distributions. This process is defined by including a suitable Beta regression framework within a generalized Dirichlet process to induce dependence among the discrete random distributions. This strategy allows for covariate dependent clustering of the observations. Some advantages of the proposed approach include wide applicability, ease of interpretation, and availability of efficient MCMC algorithms. The motivation for this work is the study of the impact of asparginage metabolism on lipid levels in a group of pediatric patients treated for acute lymphoblastic leukemia.
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Antineoplásicos/farmacologia , Asparaginase/farmacologia , Bioestatística , Interpretação Estatística de Dados , Modelos Estatísticos , Avaliação de Resultados em Cuidados de Saúde/métodos , Leucemia-Linfoma Linfoblástico de Células Precursoras/sangue , Leucemia-Linfoma Linfoblástico de Células Precursoras/tratamento farmacológico , Antineoplásicos/administração & dosagem , Asparaginase/administração & dosagem , Teorema de Bayes , Criança , Humanos , Estatísticas não ParamétricasRESUMO
Network meta-analysis (NMA) technique extends the standard meta-analysis methods, allowing pairwise comparison of all treatments in a network in the absence of head-to-head comparisons. Traditional NMA models consider a single endpoint for each trial. However, in many cases, trials in the network have different durations and/or report data at multiple time points. Moreover, these time points are often not the same for all trials. In this work, we review the most relevant methods that incorporate multiple time points and allow indirect comparisons of treatment effects across different longitudinal studies. In particular, we focus on the mixed treatment comparison developed by Dakin et al,[10] on the Bayesian evidence synthesis techniques-integrated two-component prediction developed by Ding et al,[11] and on the more recent method based on fractional polynomials by Jansen et al.[12] We highlight the main features of each model and illustrate them in simulations and in a real data application. Our study shows that methods based on fractional polynomials offer a flexible modeling strategy in most applications.
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Estudos Longitudinais , Modelos Estatísticos , Metanálise em Rede , Teorema de Bayes , Simulação por Computador , Humanos , Ensaios Clínicos Controlados Aleatórios como AssuntoRESUMO
Juvenile dermatomyositis (JDM) is a rare autoimmune disease that may lead to serious complications, even to death. We develop a 2-state Markov regression model in a Bayesian framework to characterise disease progression in JDM over time and gain a better understanding of the factors influencing disease risk. The transition probabilities between disease and remission state (and vice versa) are a function of time-homogeneous and time-varying covariates. These latter types of covariates are introduced in the model through a latent health state function, which describes patient-specific health over time and accounts for variability among patients. We assume a nonparametric prior based on the Dirichlet process to model the health state function and the baseline transition intensities between disease and remission state and vice versa. The Dirichlet process induces a clustering of the patients in homogeneous risk groups. To highlight clinical variables that most affect the transition probabilities, we perform variable selection using spike and slab prior distributions. Posterior inference is performed through Markov chain Monte Carlo methods. Data were made available from the UK JDM Cohort and Biomarker Study and Repository, hosted at the UCL Institute of Child Health.