Post date: Sep 12, 2016 9:11:36 PM
Title: Modeling Gap Times in Panel Count Data with Informative Observation Times and Unknown Time Zero: Assessing Spontaneous Labor in Women
Speaker: Rajeshwari Sundaram, Eunice Kennedy Shriver National institute of Child Health and Human Development, NIH, USA
Abstract:
Defining labor progression in women has been a long-standing challenge for obstetricians. Cervical dilation, as integer-valued measurement, is a key indicator of labor progression. Assessing the distribution of the time to per-unit increments of cervical dilation is of considerable interest in aiding obstetricians with better management of labor. Given that women are observed only intermittently for cervical dilation after they get admitted to hospital and that the observation frequency is very likely correlated to how fast/slow she dilates, one could view such data as panel count data with informative observation times and unknown time-zero. We propose semiparametric proportional rate models for the cervical dilation process and the observation process, with a multiplicative subject-specific frailty variable capturing the correlation between the two processes. Inference procedures for the gap times between consecutive events are proposed for both the scenarios with known and unknown time-zero using maximum likelihood approach and estimating equations. The methodology is assessed through simulation study and its large sample properties. A detailed analysis using the proposed method applied to the longitudinal cervical dilation data from the National Collaborative Perinatal Project from 1960s and the Consortium of Safe Labor of 2000s will be presented providing interesting comparisons across time. We will discuss other statistical challenges in studying labor progression including second stage of labor as well as labor arrests, if time permits.