Open Access
December 2013 Fitting birth–death processes to panel data with applications to bacterial DNA fingerprinting
Charles R. Doss, Marc A. Suchard, Ian Holmes, Midori Kato-Maeda, Vladimir N. Minin
Ann. Appl. Stat. 7(4): 2315-2335 (December 2013). DOI: 10.1214/13-AOAS673


Continuous-time linear birth–death-immigration (BDI) processes are frequently used in ecology and epidemiology to model stochastic dynamics of the population of interest. In clinical settings, multiple birth–death processes can describe disease trajectories of individual patients, allowing for estimation of the effects of individual covariates on the birth and death rates of the process. Such estimation is usually accomplished by analyzing patient data collected at unevenly spaced time points, referred to as panel data in the biostatistics literature. Fitting linear BDI processes to panel data is a nontrivial optimization problem because birth and death rates can be functions of many parameters related to the covariates of interest. We propose a novel expectation–maximization (EM) algorithm for fitting linear BDI models with covariates to panel data. We derive a closed-form expression for the joint generating function of some of the BDI process statistics and use this generating function to reduce the E-step of the EM algorithm, as well as calculation of the Fisher information, to one-dimensional integration. This analytical technique yields a computationally efficient and robust optimization algorithm that we implemented in an open-source R package. We apply our method to DNA fingerprinting of Mycobacterium tuberculosis, the causative agent of tuberculosis, to study intrapatient time evolution of IS6110 copy number, a genetic marker frequently used during estimation of epidemiological clusters of Mycobacterium tuberculosis infections. Our analysis reveals previously undocumented differences in IS6110 birth–death rates among three major lineages of Mycobacterium tuberculosis, which has important implications for epidemiologists that use IS6110 for DNA fingerprinting of Mycobacterium tuberculosis.


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Charles R. Doss. Marc A. Suchard. Ian Holmes. Midori Kato-Maeda. Vladimir N. Minin. "Fitting birth–death processes to panel data with applications to bacterial DNA fingerprinting." Ann. Appl. Stat. 7 (4) 2315 - 2335, December 2013.


Published: December 2013
First available in Project Euclid: 23 December 2013

zbMATH: 1283.92027
MathSciNet: MR3161724
Digital Object Identifier: 10.1214/13-AOAS673

Keywords: EM algorithm , IS6110 , missing data , transposable element , tuberculosis

Rights: Copyright © 2013 Institute of Mathematical Statistics

Vol.7 • No. 4 • December 2013
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