Study protocol and baseline characteristics of newly induced dialysis patients: a prospective multi-center cohort study with a biological sample bank, the Ibaraki Dialysis Initiation Cohort (iDIC) study
Authors: Tawara-Iida Takashi , Usui Joichi , Ebihara Itaru , Ishizu Takashi , Kobayashi Masaki , Maeda Yoshitaka , Kobayashi Hiroaki , Kobayashi Tokuro , Ueda Atsushi , Tsuchida Makoto , Sakai Shinichiro , Yamagata Kunihiro ,   and the Study Group of the Ibaraki Dialysis Initiation Cohort Study, Nakamura Hideko , Takada Kenji , Kozaki Koichi , Iwabuchi Satoshi , Iitsuka Tadashi , Nishiki Kenta , Takasaki Hideaki , Takita Takashi , Nakajima Masami , Honma Sumiko , Akai Youichi , Ishizuka Genzou , Issiki Koichi , Saito Takako , Iwamoto Hitoshi , Ohishi Akira , Ohtsuka Masakazu , Ono Atsushi , Kashiwabara Hidehiko , Kanekawa Takuro , Kanamori Naoaki , Kaneda Fumika , Kikuchi Hiroshi , Kubo Masashi , Kurosawa Hiromi , Shiraishi Takeshi , Shiigai Tatsuo , Shima Masayoshi , Takahashi Tokuo , Matsukawa Hideki , Tokoi Minoru , Tsunematsu Sadao , Tsuruta Atsushi , Deguchi Masao , Hayakawa Masahiro , Hiroi Makoto , Maeda Nobuki , Hoshino Takanobu , Yamaguchi Tetsu , Yamada Kota , Takeda Atsushi , Takahashi Ikuo , Yuhara Takamichi , Kondo Tadashi , Ooba Syoji , Ogura Yasunobu , Tachibana Hisaya , Ookawa Hiroshi , Fujii Toshihiro 
Published: March 2022

Abstract
Background
Patients with end-stage kidney disease (ESKD) face higher risks of life-threatening events including cardiovascular disease. Various risk factors are identified as agents influencing the life prognosis of ESKD patients. Herein, we evaluated the risk factors related to the outcomes of Japanese patients with dialysis induction. We present the study protocol, the patients’ baseline characteristics, and their outcomes.

Methods
The Ibaraki Dialysis Initiation Cohort (iDIC) Study is a prospective multi-center cohort study in collaboration with 60 tertiary-care facilities in Ibaraki Prefecture, Japan. We collected baseline data from clinical records and analyzed blood and urine samples of these facilities’ patients with diabetic nephropathy, hypertensive nephrosclerosis, and chronic glomerulonephritis (CGN). The study’s primary outcome was the survival rate at 24 months after dialysis induction. We performed a Kaplan-Meier analysis for cumulative survival and a Cox proportional hazards analysis for all-cause mortality and hospitalization.

Results
We analyzed 636 patients’ cases (424 males, 212 females, age 67.4 ± 13.1 yrs. [mean ± SD]). We compared the patients’ baseline data with those of similar cohort studies. As the primary kidney disease, 327 cases (51.4%) were diagnosed as diabetic nephropathy, 101 (15.9%) as hypertensive nephrosclerosis, and 114 (17.9%) as CGN. The mean serum creatinine value was 9.1 ± 2.9 mg/dL. The mean estimated glomerular filtration rate was 5.6 ± 1.8 mL/min/1.73m2. The cumulative survival rates at 6 months and 24 months after dialysis induction were 95.2 and 87.7%, respectively. The cumulative survival rate was significantly lower with increasing age. A Cox proportional hazards regression analysis demonstrated that high age was significantly associated with all-cause mortality.

Conclusions
Regarding the clinical characteristics of these newly induced dialysis patients, the same trend as in other cohort studies was observed. Another study is underway to explore prognostic factors based on the iDIC Study’s findings.