CARSK trial baseline characteristics and generalisability

The Canadian-Australasian randomised trial of screening kidney transplant candidates for coronary artery disease (CARSK) is an investigator-initiated, multicentre randomised controlled trial seeking to determine whether no-screening is inferior to regular screening. Here we describe baseline characteristics of CARSK participants across regions and assess their representativeness by comparison with contemporary waitlisted patients in Australia and New Zealand (ANZ).
Methods: Baseline characteristics were summarised overall and by region. Continuous variables across regions were compared using the Kruskal–Wallis test, and categorical variables using Pearson’s chi-square test. For external comparison, ANZ CARSK participants were compared with actively waitlisted patients in 2024 from ANZDATA using Wilcoxon signed-rank test for continuous, exact binomial tests for binary, and exact multinomial tests for categorical variables. Variables were harmonised to align definitions.
Results: A total of 3,242 CARSK participants were randomised between 2014 and 2026 (Figure 1), recruited initially as pilot participants in Canada 2014-16, then dominantly in Australia and New Zealand between 2016-2020, Canada 2019-2026 and Europe 2022-2026. Participants from North America and Europe were older than those from ANZ (median 57 vs 56 vs 53 years respectively, p<0.001) (Table 1). The proportions of male participants were similar across groups (63-67%, p=0.19). Obesity was more prevalent in ANZ and North America (32% and 33%), less in Europe (26%) (p=0.015). Diabetes as primary cause of kidney failure was more common in ANZ (28%) and North America (26%) than Europe (15%) (p<0.001). Current smoking was more frequent in Europe (11%) than ANZ (4%) and North America (6%) (p<0.001).  Comorbid diabetes and coronary artery disease was higher in North America and ANZ than in Europe. There was broad representation of ethnic minorities in all regions, including first nations people.

Compared with the 2024 ANZDATA waitlist, CARSK ANZ participants were younger (13% vs 23% aged ≥65 years, p<0.001) and had a higher proportion of diabetic kidney disease (28% vs 17%, p<0.001). Comorbid diabetes was more prevalent in CARSK ANZ, while peripheral vascular disease and coronary artery disease were more common in 2024 ANZDATA.  
Conclusion: Substantial heterogeneities were observed in baseline characteristics across regions in this 12-year multinational study, likely reflecting regional differences in waitlisted population demographics and comorbid profiles, and global changes over time, particularly increasing waitlisted age. Consistent with this hypothesis, ANZ CARSK participants recruited over a 10-year period demonstrated younger age but comparable ethnic mix and comorbid profiles compared to the 2024 ANZDATA waitlist. CARSK has enrolled a large, demographically broad cohort that should ensure generalisability of results to waitlist populations globally.