Verenryhmä

Verenryhmä (Finnish for blood group) refers to the classification of human blood by the presence or absence of specific antigens on the surface of red blood cells. The most important systems for transfusion medicine are ABO and Rh.

ABO antigens A and B form four primary phenotypes: A, B, AB and O. Individuals usually have antibodies against the ABO antigens they do not express, which means that ABO-compatible matching is essential for safe transfusion.

Rh refers to the presence (positive) or absence (negative) of the D antigen; Rh compatibility is important in both transfusion and pregnancy. Crossmatching and blood typing are performed before transfusions to prevent immune reactions.

O negative red cells are commonly used in emergencies as a universal donor, while AB positive plasma is often treated as a universal plasma donor. In clinical practice, the ABO and Rh status of both donor and recipient guides transfusion decisions to minimize the risk of hemolysis and other complications.

In pregnancy, Rh incompatibility between an Rh-negative mother and an Rh-positive fetus can cause hemolytic disease of the fetus and newborn if not managed, typically with immune globulin prophylaxis.

Beyond ABO and Rh, many other blood group systems exist (such as Kell, Duffy, Kidd, MNS) that can affect transfusion safety and prenatal care. Blood typing also uses serological methods and increasingly genetic testing to determine an individual's serotype and to detect rare variants.

The concept originates from early 20th-century work on the ABO system by Karl Landsteiner and later discoveries on the Rh factor, which together form the foundation of modern transfusion medicine.