Search results for "Markov"
showing 10 items of 628 documents
Clustering-Based Protocol Classification via Dimensionality Reduction
2015
We propose a unique framework that is based upon diffusion processes and other methodologies for finding meaningful geometric descriptions in high-dimensional datasets. We will show that the eigenfunctions of the generated underlying Markov matrices can be used to construct diffusion processes that generate efficient representations of complex geometric structures for high-dimensional data analysis. This is done by non-linear transformations that identify geometric patterns in these huge datasets that find the connections among them while projecting them onto low dimensional spaces. Our methods automatically classify and recognize network protocols. The main core of the proposed methodology…
Comparison of Different Hypotheses Regarding the Spread of Alzheimer’s Disease Using Markov Random Fields and Multimodal Imaging
2018
Alzheimer’s disease (AD) is characterized by a cascade of pathological processes that can be assessed in vivo using different neuroimaging methods. Recent research suggests a systematic sequence of pathogenic events on a global biomarker level, but little is known about the associations and dependencies of distinct lesion patterns on a regional level. Markov random fields are a probabilistic graphical modeling approach that represent the interaction between individual random variables by an undirected graph. We propose the novel application of this approach to study the interregional associations and dependencies between multimodal imaging markers of AD pathology and to compare different hy…
Optimization of anemia treatment in hemodialysis patients via reinforcement learning
2013
Objective: Anemia is a frequent comorbidity in hemodialysis patients that can be successfully treated by administering erythropoiesis-stimulating agents (ESAs). ESAs dosing is currently based on clinical protocols that often do not account for the high inter- and intra-individual variability in the patient's response. As a result, the hemoglobin level of some patients oscillates around the target range, which is associated with multiple risks and side-effects. This work proposes a methodology based on reinforcement learning (RL) to optimize ESA therapy. Methods: RL is a data-driven approach for solving sequential decision-making problems that are formulated as Markov decision processes (MDP…
Comprehensive geriatric assessment decreases prevalence of orthostatic hypotension in older persons
2013
Background: Orthostatic hypotension (OH) is associated with significant morbidity and mortality among older people. We have studied whether its prevalence can be reduced by a Comprehensive Geriatric Assessment (CGA). Study design and setting: 1000 randomly-selected persons aged ≥75 years were divided into intervention ( n = 500) and control groups ( n = 500). We focused on those subjects in whom an orthostatic blood pressure test had been performed at least once during the study period (2004–2007) ( n = 365 and 332 for intervention and control groups, respectively). A CGA, including evaluation of the adequacy of the medication, was performed annually in the intervention group but not in th…
The unobserved pattern of material hardship and health among older Americans
2019
This paper investigates the relationship between self-reported health and material hardship among older Americans. Differently from income-based measures, material hardship provides a more specific description of the concrete adversities faced by the elderly. We have used the last six waves of the Health and Retirement Study to explore the relative contributions of state dependence, unobserved heterogeneity and time-specific shocks on reporting poor health, experiencing food insecurity and medication cutbacks. We have used a Latent Markov model to estimate a multivariate non-linear system of equations for panel data allowing time-varying unobserved heterogeneity. Our results reveal a high s…
Personalized cost-effectiveness of boceprevir-based triple therapy for untreated patients with genotype 1 chronic hepatitis C
2014
Abstract Background We assessed the cost-effectiveness of boceprevir-based triple therapy compared to peginterferon alpha and ribavirin dual therapy in untreated patients with genotype 1 chronic hepatitis C; patients were discriminated according to the combination of baseline plus on-treatment predictors of boceprevir-based triple therapy. Methods Cost-effectiveness analysis performed according to data from the available published literature. The target population was composed of untreated Caucasian patients, aged 50 years, with genotype 1 chronic hepatitis C, and these were evaluated over a lifetime horizon by Markov model. The study was carried out from the perspective of the Italian Nati…
Cost-effectiveness of sorafenib treatment in field practice for patients with hepatocellular carcinoma
2013
The purpose was to assess the cost-effectiveness of sorafenib in the treatment of hepatocellular carcinoma (HCC) patients incorporating current prices and the results of the recent published field practice SOraFenib Italian Assessment (SOFIA) study. We created a Markov Decision Model to evaluate, in a hypothetical cohort of Caucasian male patients, aged 67 years with Barcelona Clinic Liver Cancer (BCLC) C HCC, or BCLC B HCC who were unfit or failed to respond to locoregional therapies, well compensated cirrhosis, and with performance status 0-1 according to Eastern Cooperative Oncology Group (ECOG), the cost-effectiveness of the following strategies: (1) full or dose-adjusted sorafenib for …
Cost-effectiveness analysis of pemetrexed versus docetaxel in the second-line treatment of non-small cell lung cancer in Spain: results for the non-s…
2010
Abstract Background The objective of this study was to conduct a cost-effectiveness evaluation of pemetrexed compared to docetaxel in the treatment of advanced or metastatic non-small cell lung cancer (NSCLC) for patients with predominantly non-squamous histology in the Spanish healthcare setting. Methods A Markov model was designed consisting of stable, responsive, progressive disease and death states. Patients could also experience adverse events as long as they received chemotherapy. Clinical inputs were based on an analysis of a phase III clinical trial that identified a statistically significant improvement in overall survival for non-squamous patients treated with pemetrexed compared …
Cost effectiveness of boceprevir or telaprevir for previously treated patients with genotype 1 chronic hepatitis C.
2013
Background & Aims Randomised controlled trials (RCTs) show that triple therapy (TT) with peginterferon alfa, ribavirin, and boceprevir (BOC) or telaprevir (TVR) is more effective than peginterferon-ribavirin dual therapy (DT) in the treatment of genotype 1 (G1) chronic hepatitis C (CHC) patients with previous relapse (RR), partial response (PAR), and null-response (NR). We assess the cost-effectiveness of TT compared to no therapy in the treatment of patients previously treated with G1 CHC. Methods The available published literature provided the data source. The target population was made up of previously treated Caucasian patients with G1 CHC and these were evaluated over a lifetime horizo…
Increased Activity of Coagulation Factor XII (Hageman Factor) Causes Hereditary Angioedema Type III
2006
International audience; Hereditary angioedema (HAE) is characterized clinically by recurrent acute skin swelling, abdominal pain, and potentially life-threatening laryngeal edema. Three forms of HAE have been described. The classic forms, HAE types I and II, occur as a consequence of mutations in the C1-inhibitor gene. In contrast to HAE types I and II, HAE type III has been observed exclusively in women, where it appears to be correlated with conditions of high estrogen levels--for example, pregnancy or the use of oral contraceptives. A recent report proposed two missense mutations (c.1032C-->A and c.1032C-->G) in F12, the gene encoding human coagulation factor XII (FXII, or Hageman factor…