Figure 1.

Flowchart of the subject selection process in this study. Briefly, 142,339 in-center maintenance hemodialysis patients, undergoing 3 sessions per week, aged 20–100 years, with duration of dialysis of 12 months or more, and without missing data in the key variables for anemia, were selected from the original data set that comprised of 301,545 living dialysis patient records. ESA, erythropoiesis-stimulating agent; Fe, serum iron; Hb, hemoglobin; HD, hemodialysis; HDF, hemodiafiltration; TIBC, total iron-binding capacity.