Preregistration Works: Increased Reporting Quality, Internal Validity, and Protocol Adherence in Animal Studies

Background: Transparency is essential for reliable research but is often compromised, contributing to irreproducibility. Preregistration can improve transparency, limit selective reporting, and prevent post hoc hypothesis changes. Despite the clear benefits of preregistration in multiple fields, its effect on reporting and quality in experimental animal studies has not been studied.Methods: We collected preregistered protocols from Preclinicaltrials.eu and Animalstudyregistry.org, along with their corresponding manuscripts and matched it with control papers to evaluate reporting quality (ARRIVE essential 10), internal validity (SYRCLE’s risk of bias tool) and deviations between protocols and manuscripts. Results: Preregistered papers (n=22) scored higher on reporting quality than controls (mean=0.794 vs 0.637 author-matched (n=13) and 0.593 journal-matched (n=20); p