Using informative prior based on expert opinion in Bayesian estimation of the transition probability matrix in Markov modelling-an example from the cost-effectiveness analysis of the treatment of patients with predominantly negative symptoms of schizophrenia with cariprazine.

BACKGROUND: When patient health state transition evidence is missing from clinical literature, analysts are inclined to make simple assumptions to complete the transition matrices within a health economic model. Our aim was to provide a solution for estimating transition matrices by the Bayesian statistical method within a health economic model when empirical evidence is lacking. METHODS: We used a previously published cost-effectiveness analysis of the use of cariprazine compared to that of risperidone in patients with predominantly negative symptoms of schizophrenia. We generated the treatment-specific state transition probability matrices in three different ways: (1) based only on the observed clinical trial data; (2) based on Bayesian estimation where prior transition probabilities came from experts' opinions; and (3) based on Bayesian estimation with vague prior transition probabilities (i.e., assigning equal prior probabilities to the missing transitions from one state to the others). For the second approach, we elicited Dirichlet prior distributions by three clinical experts. We compared the transition probability matrices and the incremental quality-adjusted life years (QALYs) across the three approaches. RESULTS: The estimates of the prior transition probabilities from the experts were feasible to obtain and showed considerable consistency with the clinical trial data. As expected, the estimated health benefit of the treatments was different when only the clinical trial data were considered (QALY difference 0.0260), its combination with the experts' beliefs were used in the economic model (QALY difference 0.0253), and when vague prior distributions were used (QALY difference 0.0243). CONCLUSIONS: Imputing zeros to missing transition probabilities in Markov models might be untenable from the clinical perspective and may result in inappropriate estimates. Bayesian statistics provides an appropriate framework for imputing missing values without making overly simple assumptions. Informative priors based on expert opinions might be more appropriate than vague priors.

Dose escalation of biologics in Crohn's disease: critical review of observational studies.

BACKGROUND: Biologics used to treat Crohn's disease (CD) may lose their effect over time, requiring dose escalation. Little information is available on this topic. AIM: To summarize rates of dose escalation, duration, de-escalation in observational studies of CD in adults treated with adalimumab, infliximab, and vedolizumab in Europe. METHODS: Two independent investigators searched Medline and Embase for observational studies published in 1998-2015 and proceedings from four major scientific meetings. Rates were summarized descriptively. RESULTS: In total, 58 articles from 12 European countries were analyzed (49 full articles, nine abstracts), providing 65 reports with 7,850 patients; 35 reported on 3,830 patients with adalimumab (ADA), and 30 on 4,020 patients with infliximab (IFX). Overall, 29.9% ± 3.5% of patients required dose escalation; 32.8% ± 6.2% with ADA and 25.2% ± 2.4% with IFX (p = .35 between drugs). Rates increased according to line of treatment: 19% for first line, 37% second, and 41% third. The median time to loss of response was 12 months, and the weighted average was 15.1 ± 5.9 months. Median time to escalation was 6.7 months; 6.7 months for ADA and 7.5 for IFX (p = .86). Short-term response rates to escalation were 63% for ADA and 45% for IFX (p = .08). There were no papers available for vedolizumab. CONCLUSIONS: A substantial proportion of patients receiving ADA or IFX for Crohn's disease require dose escalation after a short period of time.

Systematic review: treatment pattern and clinical effectiveness and safety of pharmaceutical therapies for Crohn's disease in Europe.

BACKGROUND: Although many clinical trials have been conducted in treatments of Crohn's disease (CD), whether the trial results were representative of daily practice needs to be supported by studies conducted in real-world settings. AIM: This study aims to identify how CD is treated and what are the clinical effectiveness and safety of the pharmaceutical therapies of CD in real-world settings. METHODS: A systematic literature review was conducted based on Medline®, Embase®, and Cochrane. All publications were assessed for title/abstract and full-text according to a predefined study protocol. Data were extracted and reported. RESULTS: A total of 1,998 publications were identified. Fifty studies including six publications reporting treatment pattern and 44 studies reporting clinical effectiveness and safety of pharmaceutical therapies in CD management in Europe were included. 5-Aminosalicylic acid and corticosteroids were reported to be used among 14%-74% of CD patients. Immunomodulators were used by 14%-25% and 29%-31% of CD patients as an initial and follow-up treatment, respectively. Biological therapies were used by 25%-33% of CD patients. A trend toward an increasing use of immunomodulators and biological therapies in Europe has been reported in recent years. Approximately 50% of patients achieved remission on immunomodulator or biologic treatment, although a relapse rate of up to 23% has been reported. CONCLUSION: There is a trend of treatment shift to immunomodulators and biologics in CD management. Clinical effectiveness of immunomodulators and biologics has been demonstrated, though with a lack of sustainability of the effectiveness.