Blood group is a method of classifying blood, typically based on antigens present on the surface of red blood cells.

There are currently more than 30 blood group systems recognised by the International Society of Blood Transfusion, of which the two most important are the ABO blood group system and the Rh blood group system.

Generally speaking, a person’s blood group remains unchanged after birth, with the exception of certain special circumstances, the most common of which is a bone marrow transplant. Bone marrow recipients will gradually develop the blood group of the donor.

Blood group systems play a crucial role in the medical field; transfusing a patient with an incompatible blood group is likely to cause a haemolytic reaction, leading to haemolytic anaemia, renal failure, shock and even death.

A haemolytic reaction generally refers to the abnormal breakdown and death of red blood cells.

As red blood cells in the blood are responsible for transporting oxygen to all parts of the body, a haemolytic reaction may cause tissue hypoxia; in severe cases, this can lead to the death of body tissues due to oxygen deprivation, thereby endangering the patient’s life.

The ABO blood group system was discovered in 1900 by Karl Landsteiner, an Austrian bacteriologist of American nationality.

He discovered that red blood cells from different individuals would agglutinate. By mixing the serum and red blood cells of different people in pairs, he identified three groups: A, B and C. The C group was later renamed Group O. Two years later, two of his students discovered a fourth group, namely Group AB.

The Rh blood group system, also known as the rhesus monkey blood group system, was discovered jointly by Karl Landsteiner and Alexander Solomon Wiener. As it was initially identified in the blood of rhesus monkeys, it is also referred to as the rhesus factor.

Its primary distinguishing feature is the presence or absence of the HRD antigen on the surface of red blood cells; red blood cells carrying this antigen are termed HR-positive, or HR-dominant, and are denoted as HR+; those without this antigen are termed HR-negative, or HR-recessive, and are denoted as HR-.

The HR-negative blood group is extremely rare, found in only a small proportion of the global population: approximately 15 per cent of Caucasians and just 0.3 to 0.4 per cent of Asians. The proportions among the A, B, O and AB blood groups are three to three to three to one respectively, which is why it is also known as ‘panda blood’.

Within the Rh blood group system, there is an even rarer blood type known as Rh null, with on average only one person in every 6 million possessing this blood type; it is therefore also known as ‘golden blood’. According to statistics, only 43 people worldwide have been confirmed to have this blood type.

If a person has blood group A and is Rh-positive, their blood group is denoted as A+, and the same principle applies to other blood groups.

In 1930, Landsteiner was awarded the Nobel Prize in Physiology or Medicine for his significant contributions to the blood group system.

In addition to the two blood group systems mentioned above, there are many other blood group systems, such as the Bombay blood group system (Hh), the P blood group system and the Mittenberg blood group system.

Is there such a thing as a unique blood group in the world?

An expectant mother in Nanjing, whilst undergoing a medical check-up at hospital, was found to have a blood group that did not belong to any of the existing blood group systems. Further tests revealed that she had developed a rare condition known as ABO haemolytic disease during her pregnancy; a mutation in her ABO blood group gene had resulted in the formation of an entirely new blood group.

The International Genetic Database has now included her blood type information in its records and established a new blood type subtype for her.

As this woman possesses a unique blood type, it means she can only receive blood from herself. Therefore, for safety’s sake, she must regularly store her own plasma to prepare for any potential future risks.

Given that receiving plasma incompatible with one’s own blood type could be fatal, how can one determine which blood types are safe to receive?

People with blood group AB+ can receive blood from any blood group, and are therefore known as ‘universal recipients’;

Whereas those with blood group O- are ‘universal donors’, as their blood can be donated to anyone.

Receiving large volumes of blood from different blood groups still carries a certain degree of risk, so it is best to receive blood from the same blood group as oneself.

The blood type personality theory, also known as the blood type personality doctrine, is a theory of personality that originated in Japan.

In 1927, a female university professor named Takeji Furukawa published a paper entitled ‘A Study of Temperament Based on Blood Type’, in which she first proposed the theory that a person’s personality is linked to their blood type. Upon publication, it attracted widespread attention in Japanese society; however, as her sample size at the time was fewer than 30 people, the research lacked scientific rigour. Today, this theory is primarily prevalent in Japan and South Korea.

Here, I have listed some descriptions of the personalities associated with different blood types according to the blood type personality theory; you may wish to see if they match your own characteristics. However, it should be noted that this theory has not yet been validated by the academic community and cannot be used as the sole criterion for determining personality.

People with Blood Type A

Strengths

Cautious, level-headed, meticulous, rule-abiding, relatively honest, patient, proactive and gentle in their dealings with others.

Weaknesses

Perfectionists, fussy, very stubborn, sometimes indecisive, and actually quite sensitive deep down.

People with Blood Type B

Strengths

Love of freedom, highly curious, straightforward, enthusiastic and cheerful, highly creative

Weaknesses

Lack of perseverance, self-centred, do as they please, dislike shouldering responsibility, hate being restricted

People with Blood Type AB

Strengths

Action-oriented, passionate, socially adept, able to analyse situations rationally, intelligent, highly adaptable

Weaknesses

Value their personal space; can be enigmatic at times; may come across as aloof; lack patience

People with Blood Type O

Strengths

Optimistic, positive, easy-going, have a good memory, value teamwork, and are sociable

Weaknesses

Prone to mood swings, overly pragmatic, can be conceited, and are sometimes a bit scatterbrained