Joint modeling of longitudinal and survival data with the Cox model and two-phase sampling

A common objective of cohort studies and clinical trials is to assess time-varying longitudinal continuous biomarkers as correlates of the instantaneous hazard of a study endpoint. We consider the setting where the biomarkers are measured in a designed sub-sample (i.e., case-cohort or two-phase sampling design), as is normative for prevention trials. We address this problem via joint models, with underlying biomarker trajectories characterized by a random effects model and their relationship with instantaneous risk characterized by a Cox model. For estimation and inference we extend the conditional score method of Tsiatis and Davidian (Biometrika 88(2):447–458, 2001) to accommodate the two-phase biomarker sampling design using augmented inverse probability weighting with nonparametric kernel regression. We present theoretical properties of the proposed estimators and finite-sample properties derived through simulations, and illustrate the methods with application to the AIDS Clinical Trials Group 175 antiretroviral therapy trial. We discuss how the methods are useful for evaluating a Prentice surrogate endpoint, mediation, and for generating hypotheses about biological mechanisms of treatment efficacy.     

Evaluation of a Training to Reduce Provider Bias Toward Pregnant Patients With Substance Abuse

The objective of this article is not to present a scientific or systematic study, but to provide an initial framework for designing a training workshop to enhance health practitioners’ (nurses, social workers, physicians, etc.) knowledge regarding substance abuse treatment and to decrease their bias toward substance-abusing women, particularly pregnant women in rural communities. We incorporated the 4 Transdisciplinary Foundations from the Substance Abuse and Mental Health Services Administration Competencies Model, with specific competencies targeted that related to provider bias. After the conference, 52 of the 70 participants completed a questionnaire to self-assess knowledge level and confidence in skill related to substance abuse management. Participant mean scores were statistically significantly higher following the conference than 1 week prior (p < .001) in the area of “gender difference with substance abuse,” moving from an average of 2.6 to 4.5 on a 5-point Likert scale. Our conference was successful in increasing attendees’ knowledge about gender difference and substance abuse among pregnant patients.     

Mark-specific hazard ratio model with missing multivariate marks

An objective of randomized placebo-controlled preventive HIV vaccine efficacy (VE) trials is to assess the relationship between vaccine effects to prevent HIV acquisition and continuous genetic distances of the exposing HIVs to multiple HIV strains represented in the vaccine. The set of genetic distances, only observed in failures, is collectively termed the ‘mark.’ The objective has motivated a recent study of a multivariate mark-specific hazard ratio model in the competing risks failure time analysis framework. Marks of interest, however, are commonly subject to substantial missingness, largely due to rapid post-acquisition viral evolution. In this article, we investigate the mark-specific hazard ratio model with missing multivariate marks and develop two inferential procedures based on (i) inverse probability weighting (IPW) of the complete cases, and (ii) augmentation of the IPW estimating functions by leveraging auxiliary data predictive of the mark. Asymptotic properties and finite-sample performance of the inferential procedures are presented. This research also provides general inferential methods for semiparametric density ratio/biased sampling models with missing data. We apply the developed procedures to data from the HVTN 502 ‘Step’ HIV VE trial.     

The Trouble With Triumph: Discourses of Governmentality in Mainstream Media Representations of Urban Youth

The Assets Coming Together for Youth project conducted a critical discourse analysis of mainstream media depictions of Jane-Finch to better understand the discursive strategies used to constitute urban youth. Although a substantive body of literature investigates the negative discourses, little analysis interrogates the nominally positive discourses deployed by mainstream media. The findings suggest that the sociopolitical significance of these nominally positive discourses may go uncontested and pose a challenge to communities advocating for policies to support urban youth development. These discourses are examined using governmentality theory to reveal how racialized narratives of individual triumph re/produce troubled communities.