The Karolinska Institute later appointed an external expert, Bengt Gerdin, to review the charges, comparing the results reported by Macchiarini and his collaborators to the medical record of the hospital. Gerdin's report was released by Karolinska in May 2015. Gerdin found that Macchiarini had committed research misconduct in seven out of seven papers: The findings showed he had not obtained ethical approval for the some of his operations (as claimed), and had misrepresented the result of some of those operations, as well as work he had done with animals.