title: Semiparametric profile likelihood estimation for continuous outcomes with excess zeros in a random-threshold damage-resistance model.
abstract: Continuous outcome data with a proportion of observations equal to zero (often referred to as semicontinuous data) arise frequently in biomedical studies. Typical approaches involve two-part models, with one part a logistic model for the probability of observing a zero and some parametric continuous distribution for modeling the positive part of the data. We propose a semiparametric model based on a biological system with competing damage manifestation and resistance processes. This allows us to derive a closed-form profile likelihood based on the retro-hazard function, leading to a flexible procedure for modeling continuous data with a point mass at zero. A simulation study is presented to examine the properties of the method in finite samples. We apply the method to a data set consisting of pulmonary capillary hemorrhage area in lab rats subjected to diagnostic ultrasound. Copyright © 2017 John Wiley & Sons, Ltd.
authors.affiliation: Department of Biostatistics and Computational Biology, University of Rochester, 265 Crittenden Blvd., Rochester, 14642, NY, U.S.A.
authors.forename: John D
authors.identifier: 0000-0003-4338-481X
authors.initials: JD
authors.lastname: Rice
authors.affiliation: Department of Biostatistics, University of Michigan, 1415 Washington Heights, Ann Arbor, 48104, MI, U.S.A.
authors.forename: Alex
authors.initials: A
authors.lastname: Tsodikov
mesh_terms: D000818:Animals; D002196:Capillaries / Q000528:radiation effects; D003627:Data Interpretation, Statistical; D006801:Humans; D016013:Likelihood Functions; D016015:Logistic Models; D008168:Lung / Q000098:blood supply / Q000528:radiation effects; D015233:Models, Statistical; D011336:Probability; D016016:Proportional Hazards Models; D051381:Rats; D000069453:Ultrasonic Waves / Q000009:adverse effects
keywords: damage threshold modeling; profile likelihood; retro-hazard; semicontinuous data; semiparametric methods