The present invention relates to a method for assessing (analyzing) the risk of potential adverse effects on a human patient mediated by administering a CD19xCD3 bispecific antibody to a human patient, the method comprising: the B cell to T cell ratio of the patient. Wherein a ratio of about 1:5 or less indicates a risk of a potential adverse effect on the patient, or the total number of B cells in the patient, wherein less than about 50 B cells per µl of peripheral blood Includes those indicative of the total B cell count at risk of potential adverse effects on the patient. Accordingly, the present invention relates to a method of administering a CD19xCD3 bispecific antibody to a human patient having a B:T cell ratio of about 1:5 or less and/or a total B cell count of less than about 50 B cells per 1 μl of peripheral blood (administration regimen). In this regard, the method comprises the steps of: (a) administering a first dose of said antibody during a first period； And successively (b) administering a second dose of the antibody for a second period, wherein the second dose exceeds the first dose. In some embodiments, a third dose of the antibody is administered during a third period. Such dosing regimens can be applied to a method of treating malignant CD19 positive lymphocytes or ameliorating and/or preventing adverse effects mediated by administration of the bispecific antibody. The invention also relates to the use of a CD19xCD3 bispecific antibody for the preparation of a pharmaceutical composition for use in the method of the invention. Also disclosed is a pharmaceutical package or kit comprising a first dose and a second dose and an optional third dose of the antibody as defined in the method/dosage regimen of the invention.본 발명은 CD19xCD3 이중특이적 항체를 인간 환자에게 투여하는 것에 의해 매개되는 인간 환자에 대한 잠재적 유해 효과의 위험을 평가 (분석)하는 방법에 관한 것으로, 그 방법은 상기 환자의 B 세포 대 T 세포 비를 결정하고, 이때 약 1:5 이하의 비가 상기 환자에 대한 잠재적 유해 효과의 위험을 가리키는 것, 또는 상기 환자의 총 B 세포 수를 결정하고, 이때 말초혈 1 ㎕ 당 B 세포 약 50개 미만의 총 B
