본 연구에서는 연령 데이터를 사용할 수 없거나 연구 기간 동안 Hb 농도가 3회 이상 측정되지 않은 환자를 제외했다.
For the present study, we excluded patients whose age data was not available, or whose Hb concentrations had not been measured at least three times during the study period.