There is a total of eight basic blood groups in Finland. Donors from all blood groups are needed every day because a patient is always given blood from their own blood group. A donor does not need to know their blood group when coming in to donate blood.
Blood groups are classifications that are based on the qualities of red blood cells and plasma antibodies in the blood. People's blood always belongs to one of four ABO blood groups: A, B, O or AB. Red blood cells are also tested for a Rhesus factor (RhD factor) and divided into RhD positive and RhD negative blood groups. In other words, there is a total of eight basic blood groups. The most common blood groups of Finns are A+ and O+.
"A donor does not need to know their blood group when coming in to donate blood. The blood group is examined for all donated blood and reported to the donor later," says Anu Korhonen, Laboratory Specialist.
The blood supply barometer reveals the need for your blood group
When a donor knows their blood group, they can use the Blood Service's blood supply barometer to check if their blood is needed. The barometer's drops indicate how much red blood cells and platelets are expected to be needed over the next few days. Blood Service recommends that a donor donate blood when the drop of their blood group is half full or almost empty.
Sometimes a donor can receive an invitation even when the drop is full; this is usually because patients need platelets from the donor's blood group. The platelets are only usable for five days. It is important that the blood donor arrive soon after receiving the invitation, if possible. The need is the greatest in the most common blood groups, because most patients belong to blood groups A+ and O+.
The barometer does not measure the real-time sufficiency of blood reserves at hospitals or at the Blood Service; instead, its purpose is to guide donors. The need for blood is affected by, for example, the number of blood donors in recent days, the use rate of blood at hospitals, and the estimated need for blood in the near future.
The goal for the Blood Service is to maintain a red cell reserve of five days for each blood group. This ensures an uninterrupted blood supply even in the event of a major disaster. In order to maintain safe blood reserve levels, approximately 800 blood donors are needed each weekday.
Incompatible blood may be dangerous to a patient
If a patient needs a blood transfusion, their blood group will be checked in advance at the hospital. The aim is to always give a patient blood from their own blood group. When deviating from the correct blood group, rules for transfusions between blood groups must be observed.
"Blood cells from a wrong blood group can cause a haemolytic reaction in a patient. This means that the patient's antibodies react and destroy the transferred blood cells. The reaction can be fatal," says Korhonen.
In case of an emergency, the patient is always first given O negative red blood cells, as they are suitable for everyone. Therefore, O negative blood, or so-called emergency blood, is needed more than other blood groups.