The impact of central IRB's on informed consent readability and trial adherence in SPRINT.

Background: Federal agencies have encouraged the use of central institutional review boards (CIRBs) for multi-site clinical trials. There is limited evidence supporting the use of CIRBs. Our aim is to evaluate how SPRINT sites regulated by CIRBs performed regarding informed consent readability and participant trial adherence compared to those regulated by local IRBs.
Methods: We conducted a cohort study using the SPRINT clinical trial. We collected the IRB of record from the stamped and approved 2012 informed consents from each of the sites. We defined CIRB as an IRB for more than one SPRINT site. Our outcomes were informed consent readability measured using the Flesch-Kincaid readability scale and trial adherence defined as a loss to follow-up, consent withdrawal, and missed last 3-month visit.
Results: Sixty-one percent of all SPRINT sites used a CIRB as their IRB of record. The adjusted mean grade reading level for CIRB consents was 13.4 (95% CI 12.6-13.8) compared to 12.3 (95% CI 12.1-13.1) for non CIRB consents (p = 0.07). CIRB sites had similar rates of withdrawal of consent and loss to follow-up as non-CIRB sites; subjects missing the last appointment of the study were more likely to come from sites regulated by a CIRB. The Veterans Affairs CIRB had the lowest rate of withdrawal of consent (1.9%) and the lowest rate of missed appointments (1.9%) among CIRBs.
Conclusions: Niether CIRB-regulated sites nor IRB regulated sites enforce the recommended readability level of the informed consent documents. Sites regulated by both IRBs had similar participant trial adherence.