Sociodemographic Predictors of Consent: A Protocol and Statistical Analysis Plan for a Nested Observational Study of Canadian Sites in the REVISE Trial

Background: In Canada, there is a lack of data relating sociodemographic characteristics to the likelihood of consent and clinical trial participation. Objective: The overall objective of this study is to examine the association of hospital-level sociodemographic variables with a priori informed consent rates for participation in the REVISE trial. Design: This study is a retrospective observational analysis of Canadian sites participating in the international REVISE trial. Methods: Sociodemographic characteristics for 42 hospitals participating in the REVISE trial will be supplemented by national data from the 2021 Canadian Census of Population Profile at the census tract level corresponding to the hospital's location. Hospital level information for Ontario sites will be derived from the Institute for Clinical Evaluate Sciences (ICES) database. Site clustering will be performed using latent class analysis, a flexible clustering technique that identifies meaningful subgroups based on sociodemographic variables purposively selected from data available through the Statistics Canada 2021 census profile, ICES, and hospital-reported data. Clustering analysis will be performed for all Ontario hospitals with available ICES data, followed by a separate analysis for all Canadian REVISE sites using Statistics Canada data. Concordance in the clustering of REVISE sites will be examined by comparing the assignment of hospitals to the latent classes separately identified using ICES and Statistics Canada data. If there is a high degree of agreement between the two datasets, sociodemographic predictors will be analyzed using the clusters identified through ICES for Ontario sites with the concordant classes based on Statistics Canada data for Canadian sites outsite Ontario. If there is disagreement in cluster assignment between the two datasets, separate analyses of sociodemographic factors will be conducted for Ontario sites using ICES data and for all Canadian sites using the 2021 Census Profile. Multivariate linear regression models will be used to analyze the association between hospital-level characteristics and the likelihood of a priori and deferred consent. Results: Results of this study will generate information about the relationship between informed consent to participate in a low-risk critical care clinical trial using different consent models, and socioeconomic patient characteristics at the hospital site level (e.g., educational attainment, knowledge of official languages, citizenship rates, family income, poverty, rurality and immigration patterns). Conclusions: This study will fill an evidence gap by generating information on the relationship between sociodemographic variables and the likelihood of informed consent to participate in a critical care clinical trial in Canada.