Blood groups
Blood groups describe certain molecules (antigens) present on the surfaces of red blood cells. Blood groups are inherited, so sometimes people refer to them as (genetic) markers. They are grouped together in blood group systems. The A and B antigens give rise to four different blood group systems: A, B, AB, O (the absence of both). Every human being has one of these blood groups.
The Rhesus factor is another marker used to differentiate blood groups. People whose red cells have the D antigen are Rhesus positive (RhD positive); people who do not have it are RhD negative. This gives rise to a total of eight possible blood group combinations (blood types): A positive, A negative, B positive, B negative, AB positive, AB negative, O positive and O negative.
These blood group markers are very important: not all blood is alike. Thus, it is essential that the blood groups of both donor and recipient be taken into account when a transfusion is performed.
| Blood group | Percentage distribution |
|---|---|
| A+ | 38% |
| A- | 7% |
| B+ | 8% |
| B- | 1% |
| AB+ | 4% |
| AB- | 1% |
| 0+ | 35% |
| 0- | 6% |
Video: The Blood Groups
The distribution of the different blood groups varies around the world. In Switzerland, A positive is the most common blood type, accounting for 38% of the population. O positive comes in a close second, at 35%. Another 8% of the population is B positive and 4% is AB positive, meaning that 85% of the Swiss population is RhD positive.
The A negative, O negative, AB negative and B negative blood types account for 7%, 6%, 1% and 1% of the population respectively, which Tells us that only 15% of the Swiss population is RhD negative. The blood group B, the least common blood group in Switzerland, is found almost exclusively in Central Asia.
Type O negative blood represents a particularly rare and valuable resource because it does not trigger adverse effects in any other blood group. This means that O negative blood can be safely given to any patient in an emergency.
Donors can use the Blood Supply Barometer to check the status of the reserves of their own blood type in Switzerland and, if possible, adjust the timing of their donation to reflect demand.
- People whose blood type is A+ can donate to people whose blood type is A+ or AB+. They themselves can receive O+, O-, A+ or A- donations.
- Donors whose blood type is A- can donate for people whose blood type is A+, A-, AB+ or AB-. A- individuals can receive donations of type A- or O-.
- People whose blood type is B+ are suitable donors for recipients whose blood type is AB+ or B+. They themselves can receive donations of type B+, B-, 0+ or 0-.
- Donors whose blood type is B- can donate to AB+, AB- B+ and B- recipients. They can receive B- or O- blood.
- People whose blood type is AB+ can only donate to people with the same blood type, but they can receive donations of any blood type.
- The blood of AB- donors can be given to recipients whose blood type is AB+ or AB-. AB- individuals can receive blood from any RhD negative donor.
- People whose blood is type O+ can donate to any RhD positive recipient. They can only receive donations of type O+ or O-, though.
- Donors whose blood type is O- are universal donors, because O- blood can be given to people of any blood type. However, they themselves can only receive donations that are also O-.
Blood group inheritance
Rules of inheritance and possible blood groups of children:
| Mother’s blood group | Father’s blood group | Child’s blood group |
|---|---|---|
| O | O | O |
| O | A | O or A |
| O | B | O or B |
| O | AB | A or B |
| A | A | A or O |
| A | B | A or B or O or AB |
| B | B | B or O |
| B | AB | A or B or AB |
| AB | AB | A or B or AB |
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