Blood Health Glossary

A comprehensive reference of terms used in blood health, testing, and transfusion medicine.

A

ABO Blood Group System — The primary blood classification system that categorizes blood into four types (A, B, AB, O) based on the presence or absence of A and B antigens on red blood cells.

Agglutination — The clumping together of red blood cells caused by antibodies binding to incompatible antigens, a dangerous reaction during mismatched transfusions.

Agglutinins — Antibodies in the plasma that react against incompatible blood type antigens. Type A blood has anti-B agglutinins; type B has anti-A.

Agglutinogens — Antigens found on the surface of red blood cells that determine blood type. Type A cells carry A agglutinogens; type B carry B agglutinogens.

Albumin — The most abundant protein in blood plasma, responsible for maintaining blood volume and transporting hormones, drugs, and other substances.

Anemia — A condition where blood lacks enough healthy red blood cells or hemoglobin to carry adequate oxygen to tissues. Common types include iron-deficiency, sickle cell, and aplastic anemia.

Antibody — A protein produced by the immune system that identifies and neutralizes foreign substances. In blood banking, antibodies determine transfusion compatibility.

Anticoagulant — A substance that prevents blood from clotting. Used in blood collection bags and as medication (e.g., warfarin, heparin).

Antigen — A molecule on the surface of cells that can trigger an immune response. Blood type antigens on red blood cells determine compatibility for transfusion.

Autologous Donation — The process of donating your own blood before a planned surgery so it can be transfused back to you during or after the procedure.

B

Basophil — A type of white blood cell involved in allergic reactions and inflammation. Basophils make up less than 1% of white blood cells.

Blood Bank — A facility that collects, tests, processes, and stores blood and blood components for transfusion. The term was coined in 1937 by Bernard Fantus.

Blood Component Therapy — The practice of separating whole blood into individual components (red cells, plasma, platelets) so patients receive only what they need.

Blood Typing — The process of determining a person’s ABO group and Rh factor by testing red blood cells for the presence of specific antigens.

Buffy Coat — The thin layer of white blood cells and platelets that forms between the red blood cell layer and plasma when blood is centrifuged.

C

CBC (Complete Blood Count) — The most commonly ordered blood test, measuring red blood cells, white blood cells, hemoglobin, hematocrit, and platelets.

Coagulation — The process by which blood forms clots to stop bleeding. Involves platelets and clotting factors working in a cascade.

Compatibility Testing — Laboratory procedures performed before transfusion to ensure donor blood is compatible with the recipient’s blood, including ABO/Rh typing and crossmatching.

Crossmatch — A laboratory test that mixes donor blood with recipient blood to check for adverse reactions before transfusion.

Cryoprecipitate — A blood component prepared from frozen plasma, rich in clotting factors (especially fibrinogen and Factor VIII). Used to treat hemophilia and other clotting disorders.

D

Directed Donation — A blood donation made by a specific person for use by a specific patient, often a family member.

Duffy Blood Group — A blood group system important in transfusion medicine. Duffy-negative blood is common among people of African descent and provides resistance to certain types of malaria.

E

Eosinophil — A type of white blood cell involved in fighting parasitic infections and in allergic responses. Normally makes up 1-3% of white blood cells.

Erythrocyte — The medical term for a red blood cell. Erythrocytes carry oxygen from the lungs to tissues and return carbon dioxide for exhalation.

F

Factor VIII — A clotting protein in blood that is deficient or absent in people with hemophilia A. Available as a concentrated blood product for treatment.

Febrile Reaction — A transfusion reaction characterized by fever and chills, usually caused by antibodies reacting to donor white blood cells.

Fibrinogen — A protein in blood plasma that is converted to fibrin during clotting, forming the structural framework of a blood clot.

Fresh Frozen Plasma (FFP) — Plasma separated from whole blood and frozen within hours of collection, preserving all clotting factors. Used to treat clotting disorders and massive bleeding.

G

Granulocyte — A type of white blood cell containing granules. Includes neutrophils, eosinophils, and basophils.

H

Hematocrit — The percentage of blood volume occupied by red blood cells. Normal range is approximately 38-50% for men and 36-44% for women.

Hematology — The branch of medicine concerned with the study of blood, blood-forming organs, and blood diseases.

Hemoglobin — The iron-containing protein in red blood cells responsible for carrying oxygen. Normal levels are 14-18 g/dL for men and 12-16 g/dL for women.

Hemolysis — The destruction or breakdown of red blood cells, releasing hemoglobin into the plasma. Can occur during incompatible transfusions.

Hemophilia — An inherited bleeding disorder caused by a deficiency of clotting factors. Hemophilia A involves Factor VIII; Hemophilia B involves Factor IX.

I

Immunoglobulin — A class of proteins (antibodies) produced by the immune system. Intravenous immunoglobulin (IVIG) is a blood product used to treat immune deficiencies.

K

Kell Blood Group — A blood group system containing antigens that can cause severe transfusion reactions and hemolytic disease of the newborn if mismatched.

L

Leukocyte — The medical term for a white blood cell. Leukocytes are part of the immune system and fight infections.

Leukoreduction — The process of removing white blood cells from donated blood to reduce the risk of febrile transfusion reactions and certain infections.

Lymphocyte — A type of white blood cell critical to immune function. Includes T cells, B cells, and natural killer cells.

M

MCH (Mean Corpuscular Hemoglobin) — The average amount of hemoglobin per red blood cell. Helps classify types of anemia.

MCV (Mean Corpuscular Volume) — The average size of red blood cells. Low MCV indicates microcytic anemia; high MCV indicates macrocytic anemia.

Monocyte — The largest type of white blood cell, which transforms into macrophages in tissues to engulf and destroy pathogens and dead cells.

N

Neutrophil — The most abundant type of white blood cell, making up 50-70% of all white cells. Neutrophils are the first responders to bacterial infections.

P

Packed Red Blood Cells (PRBCs) — A blood component prepared by removing most of the plasma from whole blood, concentrating the red blood cells. The most commonly transfused blood product.

Phlebotomy — The practice of drawing blood from a vein, whether for testing, donation, or therapeutic purposes.

Plasma — The liquid portion of blood, comprising about 55% of blood volume. Plasma is 95% water and carries proteins, hormones, nutrients, and waste products.

Platelet — A small cell fragment in blood essential for clotting. Platelets have a shelf life of only 5 days, making them always in demand.

R

RDW (Red Cell Distribution Width) — A measure of the variation in red blood cell size. Elevated RDW can indicate nutritional deficiencies or mixed anemias.

Rh Factor — A protein (D antigen) on the surface of red blood cells. People who have it are Rh positive; those who don’t are Rh negative.

Rh Immune Globulin (RhIg) — A blood product given to Rh-negative mothers to prevent them from developing antibodies against Rh-positive fetal blood cells.

S

Sickle Cell Disease — An inherited blood disorder where red blood cells become crescent-shaped, causing pain, organ damage, and increased infection risk.

Serum — The liquid portion of blood remaining after both cells and clotting factors are removed. Similar to plasma but without fibrinogen.

T

Thalassemia — A group of inherited blood disorders characterized by reduced hemoglobin production, leading to anemia. Most common in Mediterranean, Asian, and African populations.

Thrombocyte — Another term for platelet.

Thrombocytopenia — A condition with abnormally low platelet count (below 150,000/µL), increasing bleeding risk.

Transfusion Reaction — An adverse response to receiving blood products, ranging from mild fever to severe hemolytic reactions.

Type and Screen — A laboratory procedure that determines a patient’s ABO/Rh blood type and screens for unexpected antibodies before a potential transfusion.

U

Universal Donor — Refers to blood type O negative, whose red blood cells can theoretically be transfused to any recipient. In practice, crossmatching is still performed.

Universal Recipient — Refers to blood type AB positive, which can theoretically receive red blood cells from any donor type.

W

Whole Blood — Blood that has not been separated into components. Rarely used for transfusion today; most donations are separated into red cells, plasma, and platelets.