A method for assessing the risk of potential adverse effects for a human patient receiving a CD19×CD3 bispecific antibody is provided. The method comprises determining the total B count in the patient, and identifying a B cell number indicative of a patient at risk of potential adverse effects from the antibody. The method further provides a dosing schedule for administering the antibody to the patient identified as at risk of potential adverse effects. Also provided is a pharmaceutical package or kit comprising a first dose and a second dose, and optionally a third dose, of the CD19×CD3 bispecific antibody as defined in the methods/dosage regimen of the disclosure.