Within the realm of medical procedures, there exists a method utilized to ascertain the suitability of blood compatibility between an individual in need of a blood transfusion and a potential donor. This process involves combining red blood cells obtained from one person with the serum, which is the translucent fluid that separates from blood during the clotting process, obtained from the other individual. The presence of clumping or agglutination of the red blood cells serves as an indicator of the presence of antibodies, thereby indicating an incompatibility between the blood samples.