Statistical Methods for Unusual Count Data: Examples From Studies of Microchimerism.

Statistical Methods for Unusual Count Data: Examples From Studies of Microchimerism.
Am J Epidemiol. 2016 Oct 21;
Authors: Guthrie KA, Gammill HS, Kamper-Jørgensen M, Tjønneland A, Gadi VK, Nelson JL, Leisenring W
Abstract
Natural acquisition of small amounts of foreign cells or DNA, referred to as microchimerism, occurs primarily through maternal-fetal exchange during pregnancy. Microchimerism can persist long-term and has been associated with both beneficial and adverse human health outcomes. Quantitative microchimerism data present challenges for statistical analysis, including a skewed distribution, excess zero values, and occasional large values. Methods for comparing microchimerism levels across groups while controlling for covariates are not well established. We compared statistical models for quantitative microchimerism values, applied to simulated data sets and 2 observed data sets, to make recommendations for analytic practice. Modeling the level of quantitative microchimerism as a rate via Poisson or negative binomial model with the rate of detection defined as a count of microchimerism genome equivalents per total cell equivalents tested utilizes all available data and facilitates a comparison of rates between groups. We found that both the marginalized zero-inflated Poisson model and the negative binomial model can provide unbiased and consistent estimates of the overall association of exposure or study group with micr...

Source: Am J Epidemiol - October 20, 2016 Category: Epidemiology Authors: Guthrie KA, Gammill HS, Kamper-Jørgensen M, Tjønneland A, Gadi VK, Nelson JL, Leisenring W Tags: Am J Epidemiol Source Type: research