Blind spots: The hidden challenges of conducting multisite intervention research.

U.S. single-IRB (sIRB) policies require one central IRB to review federally funded multisite research. Although intended to support collaboration, few studies have explored the practical challenges of implementing sIRBs. Drawing on firsthand experience from a multisite project, we present challenges and solutions to inform researchers considering or required to use sIRBs. Challenges include identifying when sIRB review is needed, costs associated with sIRB review, insufficient communication pathways, and complex submission processes. Recommendations include consulting with the IRB early, proactively confirming reliance processes and needed updates, establishing expectations for clear communication across sites, increasing structural support to promote equitable participation, and standardizing local context review requirements to improve consistency and efficiency.