title: Joint assessment of dependent discrete disease state processes.
abstract: In multiple sclerosis, the primary clinical measure of disability level is an ordinal score, the expanded disability severity scale score. In relapsing-remitting multiple sclerosis, measures of relapse are additionally of interest. Multiple sclerosis patients are typically assessed with regard to both the expanded disability severity scale and relapse state at each follow-up visit. As both are discrete measures, the two can be viewed as jointly dependent Markov processes. One of the main goals of multiple sclerosis research is to accurately model, over time, both transitions between expanded disability severity scale states and change in relapse state. This objective requires a number of significant modeling decisions, including decisions about whether or not the combination of specific disease states is warranted and assessment of the dependence structure between the two disease processes. Historically, such decisions are often made in an ad hoc manner and are not formally justified. We propose novel use of Bayes factors and Bayesian variable selection in the assessment of jointly dependent Markovian processes in multiple sclerosis. Methods are assessed using both simulated data and data collected from the Partners Multiple Sclerosis Center in Boston, MA.
authors.affiliation: 1 Department of Statistics, Brigham Young University, Provo, USA.
authors.forename: David
authors.initials: D
authors.lastname: Engler
authors.affiliation: 2 Partners MS Center, Brigham and Women's Hospital, Brookline, USA.
authors.forename: Tanuja
authors.initials: T
authors.lastname: Chitnis
authors.affiliation: 3 Biostatistics Center, Massachusetts General Hospital, Boston, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Healy
mesh_terms: D001499:Bayes Theorem; D001900:Boston; D004185:Disability Evaluation; D006801:Humans; D008390:Markov Chains; D020529:Multiple Sclerosis, Relapsing-Remitting / Q000175:diagnosis* / Q000503:physiopathology*; D012008:Recurrence
keywords: Bayes factors; Bayesian variable selection; Markov processes; Ordinal transition models; model selection