title: A Bayesian prediction model between a biomarker and the clinical endpoint for dichotomous variables.
abstract: BACKGROUND
  Early biomarkers are helpful for predicting clinical endpoints and for evaluating efficacy in clinical trials even if the biomarker cannot replace clinical outcome as a surrogate. The building and evaluation of an association model between biomarkers and clinical outcomes are two equally important concerns regarding the prediction of clinical outcome. This paper is to address both issues in a Bayesian framework.
  
  
  METHODS
  A Bayesian meta-analytic approach is proposed to build a prediction model between the biomarker and clinical endpoint for dichotomous variables. Compared with other Bayesian methods, the proposed model only requires trial-level summary data of historical trials in model building. By using extensive simulations, we evaluate the link function and the application condition of the proposed Bayesian model under scenario (i) equal positive predictive value (PPV) and negative predictive value (NPV) and (ii) higher NPV and lower PPV. In the simulations, the patient-level data is generated to evaluate the meta-analytic model. PPV and NPV are employed to describe the patient-level relationship between the biomarker and the clinical outcome. The minimum number of historical trials to be included in building the model is also considered.
  
  
  RESULTS
  It is seen from the simulations that the logit link function performs better than the odds and cloglog functions under both scenarios. PPV/NPV ≥0.5 for equal PPV and NPV, and PPV + NPV ≥1 for higher NPV and lower PPV are proposed in order to predict clinical outcome accurately and precisely when the proposed model is considered. Twenty historical trials are required to be included in model building when PPV and NPV are equal. For unequal PPV and NPV, the minimum number of historical trials for model building is proposed to be five. A hypothetical example shows an application of the proposed model in global drug development.
  
  
  CONCLUSIONS
  The proposed Bayesian model is able to predict well the clinical endpoint from the observed biomarker data for dichotomous variables as long as the conditions are satisfied. It could be applied in drug development. But the practical problems in applications have to be studied in further research.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Jiang
authors.forename: Yang
authors.initials: Y
authors.lastname: Song
authors.forename: Qiong
authors.initials: Q
authors.lastname: Shou
authors.affiliation: Department of Health Statistics, School of Preventive Medicine, Fourth Military Medical University, No, 169 Changle West Road, Xi'an, Shaanxi, China. jielaixia@yahoo.com.
authors.forename: Jielai
authors.initials: J
authors.lastname: Xia
authors.forename: William
authors.initials: W
authors.lastname: Wang
mesh_terms: D001499:Bayes Theorem; D015415:Biomarkers / Q000032:analysis*; D002986:Clinical Trials as Topic / Q000379:methods / Q000706:statistics & numerical data*; D003198:Computer Simulation; D003627:Data Interpretation, Statistical; D023381:Endpoint Determination; D006801:Humans; D015233:Models, Statistical; D011237:Predictive Value of Tests; D011379:Prognosis; D012107:Research Design / Q000706:statistics & numerical data*
chemical_list: D015415:Biomarkers