Clinical chemistry the denser blood cells and platelets to the bottom of the centrifuge tube, leaving the liquid serum fraction resting above the packed cells. This initial step before analysis has recently been included in instruments that operate on the "integrated system" principle. Plasma is in essence the same as serum, but is obtained by centrifuging the blood "without" clotting. Plasma is obtained by centrifugation "before" clotting occurs. The type of test required dictates what type of sample is used. A large medical laboratory will accept samples for up to about 700 different kinds of tests. Even the largest of laboratories rarely
Blood transfusion Blood transfusion Blood transfusion is generally the process of receiving blood or blood products into one's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but modern medical practice commonly uses only components of the blood, such as red blood cells, white blood cells, plasma, clotting factors, and platelets. Red blood cells contain hemoglobin and increase iron levels by improving the amount of oxygen found in the body. White blood cells, are not commonly used during transfusion but are related to the immune system and to fight infections.