Ustekinumab trough concentrations predict clinical remission in perianal fistulizing crohn's disease: a real-world retrospective cohort study. - Liu, Xiaoyu; Yan, Yuehua; Yi, Jiaqin; Luo, Dongmei; Geng, Jun; Huang, Huixian; Wang, Jingjing; Gu, Yunfei; Yang, Bolin; Gong, Yuxia; Wang, Hao (BMC Gastroenterology, 2025)