title: A non-parametric model to address overdispersed count response in a longitudinal data setting with missingness.
abstract: Count responses are becoming increasingly important in biostatistical analysis because of the development of new biomedical techniques such as next-generation sequencing and digital polymerase chain reaction; a commonly met problem in modeling them with the popular Poisson model is overdispersion. Although it has been studied extensively for cross-sectional observations, addressing overdispersion for longitudinal data without parametric distributional assumptions remains challenging, especially with missing data. In this paper, we propose a method to detect overdispersion in repeated measures in a non-parametric manner by extending the Mann-Whitney-Wilcoxon rank sum test to longitudinal data. In addition, we also incorporate the inverse probability weighted method to address the data missingness. The proposed model is illustrated with both simulated and real study data.
authors.affiliation: 1 Department of Biostatistics, St Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Hui
authors.initials: H
authors.lastname: Zhang
authors.affiliation: 2 Department of Biostatistics and Computational Biology and Department of Psychiatry, University of Rochester, Rochester, NY, USA.
authors.forename: Hua
authors.initials: H
authors.lastname: He
authors.affiliation: 2 Department of Biostatistics and Computational Biology and Department of Psychiatry, University of Rochester, Rochester, NY, USA.
authors.forename: Naiji
authors.initials: N
authors.lastname: Lu
authors.affiliation: 1 Department of Biostatistics, St Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Zhu
authors.affiliation: 3 Division of Biostatistics, Office of Surveillance and Biometrics, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Bo
authors.initials: B
authors.lastname: Zhang
authors.affiliation: 3 Division of Biostatistics, Office of Surveillance and Biometrics, Center for Devices and Radiological Health, Food and Drug Administration, Silver Spring, MD, USA.
authors.forename: Zhiwei
authors.initials: Z
authors.lastname: Zhang
authors.affiliation: 1 Department of Biostatistics, St Jude Children's Research Hospital, Memphis, TN, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Tang
mesh_terms: D000293:Adolescent; D005260:Female; D006801:Humans; D016015:Logistic Models; D008137:Longitudinal Studies; D008297:Male; D016012:Poisson Distribution; D011336:Probability; D012107:Research Design; D012725:Sexual Behavior / Q000706:statistics & numerical data*; D018709:Statistics, Nonparametric; D047568:Unsafe Sex / Q000706:statistics & numerical data
keywords: Count response; U-statistics; inverse probability weighted estimate; missing data; overdispersion