Figure 1. Flow chart of data collection during the study for 398 asymptomatic patients admitted for investigation of the cause of IDA.

BDE, bidirectional endoscopy; EGD, esophagogastroduodenoscopy; GI, gastrointestinal; Hb, hemoglobin; IDA, iron deficiency anemia; MCV, mean corpuscular volume; TIBC, total iron-binding capacity; TS, transferrin saturation; WHO, World Health Organization.

^aAll GI endoscopic procedures utilized the Pentax Medical (HOYA Group, Shinjuku, Tokyo) or Olympus (Olympus Surgical Technologies America, Southborough, MA) endoscopic system.

^bWhen the EGD and colonoscopy were done on the same day or in different days up to four weeks apart.