Analysis of clinical trial registry entry histories using the novel R package cthist.

Historical clinical trial registry data can only be retrieved by manually accessing individual clinical trials through registry websites. This limits the feasibility, accuracy and reproducibility of certain kinds of research on clinical trial activity and presents challenges to the transparency of the enterprise of human research. This paper presents cthist, a novel, free and open source R package that enables automated scraping of clinical trial registry entry histories and returns structured data for analysis. Documentation of the implementation of the package cthist is provided, as well as 3 brief case studies with example code.