Shahrokhabadi, Mohadeseh ShojaeiChen, Ding-Geng (Din)Mirkamali, Sayed JamalKazemnejad, AnoshirvanZayeri, Farid2022-05-242022-05-242021-10-15Shahrokhabadi, M.S.; Chen, D.-G.; Mirkamali, S.J.; Kazemnejad, A.; Zayeri, F. Marginalized Two-Part Joint Modeling of Longitudinal Semi-Continuous Responses and Survival Data: With Application to Medical Costs. Mathematics 2021, 9, 2603. https://DOI.org/10.3390/math9202603.2227-739010.3390/math9202603https://repository.up.ac.za/handle/2263/85642Non-negative continuous outcomes with a substantial number of zero values and incomplete longitudinal follow-up are quite common in medical costs data. It is thus critical to incorporate the potential dependence of survival status and longitudinal medical costs in joint modeling, where censorship is death-related. Despite the wide use of conventional two-part joint models (CTJMs) to capture zero-inflation, they are limited to conditional interpretations of the regression coefficients in the model’s continuous part. In this paper, we propose a marginalized two-part joint model (MTJM) to jointly analyze semi-continuous longitudinal costs data and survival data. We compare it to the conventional two-part joint model (CTJM) for handling marginal inferences about covariate effects on average costs. We conducted a series of simulation studies to evaluate the superior performance of the proposed MTJM over the CTJM. To illustrate the applicability of the MTJM, we applied the model to a set of real electronic health record (EHR) data recently collected in Iran. We found that the MTJM yielded a smaller standard error, root-mean-square error of estimates, and AIC value, with unbiased parameter estimates. With this MTJM, we identified a significant positive correlation between costs and survival, which was consistent with the simulation results.en© 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license.Zero-inflatedRight-skewedSemi-continuousProportional hazards modelMedical costs dataConventional two-part joint models (CTJMs)Marginalized two-part joint model (MTJM)Electronic health record (EHR)Article