Citation
Zivich, Paul N.; Edwards, Jessie K.; Lofgren, Eric T.; Cole, Stephen R; Shook-Sa, Bonnie E.; & Lessler, Justin (2024). Transportability without Positivity: A Synthesis of Statistical and Simulation Modeling. Epidemiology, 35(1), 23-31.Abstract
Studies designed to estimate an effect of an action in a randomized or observational often do not represent a random sample of the desired target population. Instead, estimates from that study can be transported to the target population. However, transportability methods generally rely on a positivity assumption, such that all relevant covariate patterns in the target population are also observed in the study sample. Strict eligibility criteria, particularly in the context of randomized trials, may lead to violations of this assumption. Two common approaches to address positivity violations are restricting the target population and restricting the relevant covariate set. As neither of these restrictions are ideal, we instead propose a synthesis of statistical and simulation models to address positivity violations. We propose corresponding g-computation and inverse probability weighting estimators. The restriction and synthesis approaches to addressing positivity violations are contrasted with a simulation experiment and an illustrative example in the context of sexually transmitted infection testing uptake. In both cases, the proposed synthesis approach accurately addressed the original research question when paired with a thoughtfully selected simulation model. Neither of the restriction approaches were able to accurately address the motivating question. As public health decisions must often be made with imperfect target population information, model synthesis is a viable approach given a combination of empirical data and external information based on the best available knowledge.URL
http://dx.doi.org/10.1097/ede.0000000000001677Reference Type
Journal ArticleYear Published
2024Journal Title
EpidemiologyAuthor(s)
Zivich, Paul N.Edwards, Jessie K.
Lofgren, Eric T.
Cole, Stephen R
Shook-Sa, Bonnie E.
Lessler, Justin
Article Type
RegularORCiD
Edwards, J -0000-0002-1741-335XZivich - 0000-0002-9932-1095
Lessler - 0000-0002-9741-8109