A medicament for treating a patient who cannot be cured with a medicament comprising as an active ingredient an antibody composition produced by a cell unresistant to a lectin which recognizes a sugar chain in which 1-position of fucose is bound to 6-position of N-acetylglucosamine in the reducing end through .alpha.-bond in a complex N-glycoside-linked sugar chain, which comprises as an active ingredient an antibody composition produced by a cell resistant to a lectin which recognizes a sugar chain in which 1-position of fucose is bound to 6-position of N-acetylglucosamine in the reducing end through .alpha.-bond in a complex N-glycoside-linked sugar chain, and a method for screening the patient by using the medicament.