Blood bag system and blood treatment method

A blood treatment method comprising:

• a centrifugation process of centrifuging whole blood or a blood component in a first bag into a light specific gravity blood component, a medium specific gravity blood component, and a heavy specific gravity blood component for each specific gravity, wherein a specific gravity of the medium specific gravity blood component is higher than a specific gravity of the light specific gravity blood component and lower than a specific gravity of the heavy specific gravity blood component;
• a first transfer process of transferring one of two blood components from among the light specific gravity blood component, the medium specific gravity blood component, and the heavy specific gravity blood component from the first bag to a second bag through a first transfer tube, and transferring the other one of the two blood components from the first bag to a third bag through a second transfer tube;
• and
• a second transfer process of transferring an added solution stored in a fourth bag to the medium specific gravity blood component through a third transfer tube while a centrifugal force is applied after the first transfer process to discharge the light specific gravity blood component remaining in the medium specific gravity blood component, thereby obtaining a washed medium specific gravity blood component.

A blood bag system comprising:

• a first bag for storing whole blood or a blood component;
• a second bag and a third bag for storing two blood components, respectively, from among a first blood component, a second blood component, and a third blood component obtained by centrifuging a content liquid in the first bag;
• a first transfer tube for connecting the first bag and the second bag to each other and transferring one blood component of the two blood components from the first bag to the second bag;
• a second transfer tube for connecting the first bag and the third bag to each other and transferring the other blood component of the two blood components from the first bag to the third bag;
• a fourth bag storing an added solution;
• and
• a third transfer tube for transferring the added solution from the fourth bag to the second blood component,
• wherein a centrifugal force acts in a transfer completed state in which the two blood components are separately transferred to the second bag and the third bag, respectively, and the added solution is transferred from the fourth bag to the second blood component through the third transfer tube, thereby discharging the first blood component remaining in the second blood component.