Non-Markov Multistate Modeling Using Time-Varying Covariates, with Application to Progression of Liver Fibrosis due to Hepatitis C Following Liver Transplant

University of California, San Francisco, CA, USA.
The International Journal of Biostatistics (Impact Factor: 1.28). 01/2010; 6(1):Article 7. DOI: 10.2202/1557-4679.1213
Source: PubMed

ABSTRACT Multistate modeling methods are well-suited for analysis of some chronic diseases that move through distinct stages. The memoryless or Markov assumptions typically made, however, may be suspect for some diseases, such as hepatitis C, where there is interest in whether prognosis depends on history. This paper describes methods for multistate modeling where transition risk can depend on any property of past progression history, including time spent in the current stage and the time taken to reach the current stage. Analysis of 901 measurements of fibrosis in 401 patients following liver transplantation found decreasing risk of progression as time in the current stage increased, even when controlled for several fixed covariates. Longer time to reach the current stage did not appear associated with lower progression risk. Analysis of simulation scenarios based on the transplant study showed that greater misclassification of fibrosis produced more technical difficulties in fitting the models and poorer estimation of covariate effects than did less misclassification or error-free fibrosis measurement. The higher risk of progression when less time has been spent in the current stage could be due to varying disease activity over time, with recent progression indicating an "active" period and consequent higher risk of further progression.

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Recurrence of hepatitis C virus (HCV) infection following liver transplantation is a major source of morbidity and mortality. The natural history of hepatitis C in the transplant setting is shortened. Overall, one third of HCV-infected recipients have developed allograft cirrhosis due to HCV recurrence by the 5(th)-7(th) year post-transplantation. The most significant variables which determine disease progression are the use of organs from old donors, the use of an inadequate immunosuppression (too low, inducing treatment rejection episodes, too potent or too rapidly changing), and the presence of comorbid conditions that also impact the quality of the graft (biliary complications, metabolic syndrome). The only factor consistently shown to modify the natural history of recurrent disease is antiviral therapy. A sustained viral response, achieved by one third of those treated with dual therapy, is associated with improved histology, reduced liver-related complications and increased survival. Variables associated with enhanced viral response with dual therapy include an adequate genetic background (IL28B C/C of both donor and recipient), good treatment adherence (full doses of ribavirin, treatment duration), lack of graft cirrhosis at baseline, and viral genotype non-1. Data with triple therapy are encouraging. Response rates of about 60% at end-of-therapy have been described. Drug-drug interactions with calcineurin inhibitors are present but easily manageable with strict trough levels monitoring. Side effects are frequent and severe, particularly anemia, infections and acute renal insufficiency. In the future new oral antivirals will likely prevent viral reinfection. In this review, we will cover the most significant but also controversial aspects regarding recurrent HCV infection, including the natural history, retransplantation, antiviral therapy, and outcome in HIV-HCV patients.
    Annals of Gastroenterology 03/2013; 26(4):304-313.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Liver fibrosis results from an excessive wound healing response in most chronic liver diseases, such as hepatitis C. Despite great advances in antiviral therapy in recent years, progressive liver fibrosis remains a major problem for patients with recurrent hepatitis C after liver transplantation. Liver biopsy remains a central tool in the management of HCV-positive liver transplant recipients, but reliable non-invasive methods for the assessment of liver fibrosis, such as ultrasound elastography, are increasingly being incorporated in the management of post-transplant patients, helping to predict prognosis, guide treatment decisions, and stratify patients for emerging antifibrotic therapies. In this review, we will review the natural history as well as tools to monitor fibrosis progression in the HCV-positive liver transplant recipient, the mechanisms underlying rapid fibrosis progression in up to 30% of these patients, the effect of antiviral therapies and highlight promising antifibrotic approaches.
    Journal of Hepatology 12/2012; DOI:10.1016/j.jhep.2012.12.014 · 10.40 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Observational cohort studies of individuals with chronic disease provide information on rates of disease progression, the effect of fixed and time-varying risk factors, and the extent of heterogeneity in the course of disease. Analysis of this information is often facilitated by the use of multistate models with intensity functions governing transition between disease states. We discuss modeling and analysis issues for such models when individuals are observed intermittently. Frameworks for dealing with heterogeneity and measurement error are discussed including random effect models, finite mixture models, and hidden Markov models. Cohorts are often defined by convenience and ways of addressing outcome-dependent sampling or observation of individuals are also discussed. Data on progression of joint damage in psoriatic arthritis and retinopathy in diabetes are analysed to illustrate these issues and related methodology.
    Statistics in Biosciences 05/2013; DOI:10.1007/s12561-013-9087-8

Full-text (2 Sources)

Available from
Jun 1, 2014