What does positive blood type mean

Blood Types Explained - A, B, AB and O

How Blood Type Is Determined And Why You Need To Know

Blood types are determined by the presence or absence of certain antigens – substances that can trigger an immune response if they are foreign to the body. Since some antigens can trigger a patient's immune system to attack the transfused blood, safe blood transfusions depend on careful blood typing and cross-matching. Do you know what blood type is safe for you if you need a transfusion?

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There are four major blood groups determined by the presence or absence of two antigens, A and B, on the surface of red blood cells. In addition to the A and B antigens, there is a protein called the Rh factor, which can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-).

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There are very specific ways in which blood types must be matched for a safe transfusion. The right blood transfusion can mean the difference between life and death. Use the interactive graphic below to learn more about matching blood types for transfusions.

Also, Rh-negative blood is given to Rh-negative patients, and Rh-positive or Rh-negative blood may be given to Rh-positive patients. The rules for plasma are the reverse.

The universal red cell donor has Type O negative blood.
The universal plasma donor has Type AB blood.

There are more than 600 other known antigens, the presence or absence of which creates "rare blood types." Certain blood types are unique to specific ethnic or racial groups. That’s why an African-American blood donation may be the best hope for the needs of patients with sickle cell disease, many of whom are of African descent. Learn about blood and diversity.

Universal donors are those with an O negative blood type. Why? O negative blood can be used in transfusions for any blood type.

Type O is routinely in short supply and in high demand by hospitals – both because it is the most common blood type and because type O negative blood is the universal blood type needed for emergency transfusions and for immune deficient infants.

Approximately 45 percent of Caucasians are type O (positive or negative), but 51 percent of African-Americans and 57 percent of Hispanics are type O. Minority and diverse populations, therefore, play a critical role in meeting the constant need for blood.

Types O negative and O positive are in high demand. Only 7% of the population are O negative. However, the need for O negative blood is the highest because it is used most often during emergencies. The need for O+ is high because it is the most frequently occurring blood type (37% of the population).

The universal red cell donor has Type O negative blood. The universal plasma donor has Type AB blood. For more about plasma donation, visit the plasma donation facts.

Nearly 16 million blood components are transfused each year in the U.S."
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There are more than 600 other known antigens, the presence or absence of which creates "rare blood types." Your blood type is considered rare if you lack antigens that 99% of the people are positive for. If you somehow lack an antigen that 99.99% are positive for, your blood type is extremely rare.

It’s inherited. Like eye color, blood type is passed genetically from your parents. Whether your blood group is type A, B, AB or O is based on the blood types of your mother and father.

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* Note: If you have questions about paternity testing or about blood group inheritance, your primary care physician should be able to provide you with an appropriate referral. Testing difficulties can cause exceptions to the above patterns. ABO blood typing is not sufficient to prove or disprove paternity or maternity.

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Rh factor blood test - Mayo Clinic

Overview

Rh factor is an inherited protein found on the surface of red blood cells. If your blood has the protein, you're Rh positive. If your blood doesn't have the protein, you're Rh negative. The "+" or "–" you might see after your blood type refers to Rh positive or Rh negative.

Rh positive is much more common than Rh negative. Having an Rh negative blood type is not an illness, and it usually does not affect your health. But it can affect pregnancy. Your pregnancy needs special care if you're Rh negative and your baby is Rh positive. That's called Rh incompatibility. A baby can inherit the Rh factor from either parent.

Your health care provider will advise that you have a blood type and Rh factor screening test during your first prenatal visit. This will show whether you are Rh positive or Rh negative.

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Why it's done

During pregnancy, problems can happen if you're Rh negative and your baby is Rh positive. Usually, your blood doesn't mix with your baby's blood during pregnancy. However, a small amount of your baby's blood could come in contact with your blood when the baby is born. It can also happen if you have bleeding or trauma to your abdomen during pregnancy.

If you're Rh negative and your baby is Rh positive, your body might produce proteins called Rh antibodies if your blood and the baby's blood mix. Those antibodies aren't a problem during the first pregnancy. But problems can happen if you become pregnant again.

If your next baby is Rh positive, the Rh antibodies can cross the placenta and damage the baby's red blood cells. This could lead to life-threatening anemia, a condition in which red blood cells are destroyed faster than the baby's body can replace them. Red blood cells are needed to carry oxygen throughout the body.

If you're Rh negative, you might need to have another blood test — called an antibody screen — several times: during your first trimester, during week 28 of pregnancy and when your baby is born. Some people need the test more often.

That test is used to detect antibodies to Rh positive blood. If you haven't started to produce Rh antibodies, you'll likely need a shot (injection) of a blood product called Rh immune globulin. This prevents your body from producing Rh antibodies during your pregnancy.

If your baby is born Rh negative, you don't need any other treatment. If your baby is born Rh positive, you'll need another injection shortly after delivery.

If you're Rh negative and your baby might be or is Rh positive, your health care provider may recommend an Rh immune globulin injection after situations in which your blood could come into contact with the baby's blood, including:

Miscarriage
Ectopic pregnancy — when a fertilized eggs implants somewhere outside the uterus, usually in a fallopian tube
Abortion
Removal of a molar pregnancy — a noncancerous (benign) tumor that develops in the uterus
Amniocentesis — a prenatal test in which a sample of the fluid that surrounds and protects a baby in the uterus (amniotic fluid) is removed for testing or treatment
Chorionic villus sampling — a prenatal test in which a sample of the wispy projections that make up most of the placenta (chorionic villi) is removed for testing
Cordocentesis — a prenatal test in which a sample of the baby's blood is removed from the umbilical cord for testing
Bleeding during pregnancy
Injury or other trauma to your abdomen during pregnancy
The external manual rotation of a baby in a breech position — such as buttocks first — before labor
Delivery

If the antibody screen shows that you're already producing antibodies, an injection of Rh immune globulin won't help. Your baby will be carefully monitored during your pregnancy. The baby might be given a blood transfusion through the umbilical cord during pregnancy or immediately after delivery if necessary.

Mother's Rh factor	Father's Rh factor	Baby's Rh factor	Precautions
Rh positive	Rh positive	Rh positive	None
Rh negative	Rh negative	Rh negative	None
Rh positive	Rh negative	Could be Rh positive or Rh negative	None
Rh negative	Rh positive	Could be Rh positive or Rh negative	Rh immune globulin injections

What you can expect

An Rh factor test is a basic blood test. The blood sample usually is taken during the first prenatal visit and sent to a lab for testing. No special preparation is necessary.

Results

If you're Rh positive, you don't need to do anything.

If you're Rh negative and your baby is Rh positive, your body could make antibodies that might be harmful during another pregnancy. Take these steps:

If you have vaginal bleeding any time during pregnancy, contact your health care provider right away.
Talk with your health care provider about scheduling an Rh immune globulin injection during your pregnancy.
Remind your health care team during labor that you're Rh negative.

By Mayo Clinic Staff

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About Blood Types - Blood Center

When a doctor talks about your blood type, he usually means two things: your ABO blood type and your Rh (rhesus factor).

A person's blood group is determined by antigens found on his red blood cells. An antigen is a structure on the surface of a cell. If it is foreign to the body, then the human defense system will react to it. Therefore, it is necessary to take into account blood groups when transfusing: the donor's blood group is determined at the Blood Center, and the patient's blood group is determined before transfusion.

AB0 system

The most important is the ABO blood group system, according to which blood is divided into groups A, B, O and AB. It is determined by two antigens located on the surface of red blood cells:

group A - only antigen A is present on the surface of erythrocytes
group B - only antigen B is present on the surface of erythrocytes
group AB - both A and B antigens are present on the surface of erythrocytes
group O - on the surface of erythrocytes there is neither antigen A nor antigen B.

If a person has blood type A, B or 0, then in his blood plasma there are also antibodies that destroy those antigens that the person himself does not have. Examples: If you have type A blood, then you cannot be transfused with type B blood, because in this case there are antibodies in your blood that fight against B antigens. If you have blood type 0, then your blood contains antibodies that fight like against antigens A and against antigens B.

If a person has blood type AB, then he does not have such antibodies, so he can be transfused with blood of any group. Therefore, the carrier of the AB blood group can be called universal patient.

A carrier of blood type 0 with a negative Rh factor, in turn, is called a universal donor, , since his red blood cells are suitable for all patients.

Rhesus (Rh ) accessory

Rh factor (Rh) can be positive (+) and negative (-). It depends on the presence of the D antigen on the surface of the red blood cells. If the D antigen is present, the person is considered Rh-positive, and if the D antigen is absent, then the person is Rh-negative.

If a person is Rh negative, contact with Rh positive blood (for example, during pregnancy or blood transfusion) may form antibodies. These antibodies can cause pregnancy problems in an Rh-negative woman if she is carrying an Rh-positive baby.

In addition to the ABO and Rh systems, about thirty more blood group systems have been discovered to date. Clinically, the most important of these are the Kell, Kidd and Duffy systems. According to the Kell system, donor blood is also examined.

How is the blood type determined?

To determine the blood type, it is mixed with a reagent containing known antibodies.

Three drops of blood taken from one person are applied to the base: the anti-A test reagent is added to one drop, the anti-B test reagent to the other, and the anti-D test reagent to the third, i.e. Rh test reagent. If blood clots form in the first drop, i.e. erythrocytes stick together (agglutination), then the person has antigen A. If erythrocytes do not stick together in another drop, therefore the person does not have antigen B; and if agglutination occurs in the third drop, then this indicates a positive Rh factor. In this example, the donor has blood type A and is Rh positive.

Donor and recipient blood group compatibility is extremely important, otherwise the recipient may have dangerous reactions to the blood transfusion.

Inheritance of blood groups

A person inherits from his father and from his mother to the same extent. Therefore, the hereditary substance has a double structure: one part from the mother and the other from the father. Speaking about the inheritance of blood groups, it must be borne in mind that:

Most of our genes exist in two copies
Each parent gives (based on a random selection) one of these copies to their children
Genes occur in different versions (alleles)
Some versions of the gene are stronger than others

ABO system

System Rh

In the AB0 system, antigens are presented in three versions A, B and 0.

Given that the hereditary substance consists of two parts, six different combinations can occur:

Genes
AA
A0
AB
B0
BB
00

The stronger part appears, both equally or a combination. In the AB0 system, genes A and B are stronger than 0, which affects the formation of the blood group as follows:

Genes	Blood type
AA	A
A0	A
AB	AB
B0	B
BB	B
00	0

Example: The mother has a combination of A0 genes in hereditary substance, and her blood type is A (at the same time, she is a carrier of the blood type 0 gene, and there is a possibility that she will pass it on to her child). The father's blood type has the designation 0, and in his hereditary substance there is a combination of genes 00. Accordingly, he can only pass 0 to the child, i.e. absence of antigens. Thus, their child may have an A (A0) or 0 (00) blood type.

In the Rh system, things are somewhat simpler, since there are only two options: the D antigen is either present (Rh positive) or absent (Rh negative). A positive Rh factor dominates a negative one.

Genes	Blood type
+/+	positive
+/-	positive
-/-	negative

Example: if the mother has Rh positive blood, and there is a hidden negative version, that is, the allele (+/-), and the father has exactly the same combination, and they both pass the negative allele, then two Rh-positive parents can have a child with a negative Rh factor.

Blood type and Rh factor

A comprehensive study that allows you to assess the belonging of the patient's blood to one of the groups according to the ABO system and determine the presence / absence of the Rh antigen.

Synonyms Russian

ABO blood type, Rh-factor.

Synonyms English

Blood typing, ABO group, Rh type.

Research method

Agglutination test.

What biomaterial can be used for research?

Venous blood.

How to properly prepare for an examination?

Eliminate fatty foods for 24 hours before the test.

General information about the study

Each person has a unique combination of antigens on the surface of their cells, including red blood cells. To date, more than 250 erythrocyte antigens are known, forming about 30 antigenic systems. In clinical terms, the most important of these are the ABO system and the Rhesus system.

The ABO system is the main blood compatibility system. It is represented by agglutinogens A and B, which are glycoproteins and located on the surface of erythrocytes, and alpha and beta agglutinins, belonging to the class of IgM immunoglobulins and circulating in blood plasma. Depending on the combination of these agglutinogens and agglutinins, 4 blood groups are distinguished according to the ABO system.

The first (I) blood group (the most common in the European population, 42% of the population) is also called the O-group, in which agglutinogens A or B are absent on the surface of red blood cells, agglutinins alpha and beta are detected in plasma.

The second (II) blood group (37%) is also called A-group, agglutinogen A is present on the surface of red blood cells, and agglutinin beta is detected in plasma.

Third (III) blood group (13% of the population) also called B-blood group, agglutinogen B is present on the surface of red blood cells, agglutinin alpha is detected in plasma.

The fourth (IV) blood group (the rarest, only 8% of the population) is also called the AB-blood group, agglutinogens of both types A and B are present on the surface of red blood cells, and agglutinins alpha and beta are absent in plasma.

The Rh system also consists of several antigens, the main of which is called the D antigen, or Rh factor. Approximately 85% of people on the surface of red blood cells can detect Rh factor (Rh-positive blood).

The belonging of human blood to a certain group according to the ABO system and the Rhesus system is genetically determined and does not change throughout life.

Determining the blood group and Rh factor is of the greatest importance in preparing for a blood transfusion. Such a need may arise in case of severe blood loss, severe forms of hemolytic anemia, diseases of the bone marrow with a violation of the normal production of red blood cells, as well as during major surgical operations. The blood group according to the ABO system and the Rh system is taken into account not only when transfusing erythrocyte mass, but also when transfusing other blood components (platelet mass, leukocyte suspension, etc. ). Determining the blood group is a mandatory test during pregnancy. In this case, data on the patient's blood group and, in some cases, on the blood group of the child's father, are taken into account for the timely diagnosis and treatment of an immunological conflict (due to the incompatibility of the blood of the fetus and mother) and the resulting hemolysis of fetal erythrocytes. Military personnel, fighters of the Ministry of Emergency Situations and other law enforcement agencies are also subject to mandatory examination for blood group and Rh factor.

It should be noted that in clinical practice several methods are used to confirm the compatibility of the blood of the donor and the recipient, including separate laboratory determination of the blood group of the donor and the recipient, a test for the individual compatibility of the donor's erythrocytes and the recipient's serum, a biological sample. These activities are carried out because the probability of error in the laboratory determination of the blood group is small, but still exists.

Since the laboratory method for determining blood groups is based on the agglutination reaction, the presence in the patient's serum of specific proteins (M-protein, cold antibodies) or some bacteria that prevent this reaction can lead to false positive or false negative results. Also, taking certain medications can affect the results of determining the Rh factor. Therefore, special attention should be paid to preparing for the test.

What is research used for?

To determine whether a person's blood group belongs to one of the groups according to the ABO system and the Rh system.

When is the test scheduled?

When transfusing blood components to a recipient;
when donating blood;
in preparation for surgery;
when planning pregnancy or during pregnancy;
for suspected fetal erythroblastosis;
in preparation for transplantation of bone marrow, kidney, liver and other organs and tissues;
when entering the military service, in the ranks of the Ministry of Emergency Situations and other law enforcement agencies.

What do the results mean?

ABO blood typing results
Agglutinogens on the surface of erythrocytes	Serum agglutinins	Blood type, Roman numerals	Blood group in Latin letters
None	Alpha and Beta	I	-
A	Beta	II	A
B	Alpha	III	B
AB	None	IV	AB

Rh results
Rh factor on the surface of erythrocytes
Found	Rh-positive blood, Rh+
Not found	Rh-negative blood, Rh-

What can influence the result?

Certain medicines (levodopa, methyldopa) may cause false positive Rh test results.

Important Notes

To obtain an accurate result, you must follow the test preparation guidelines.
The belonging of human blood to a certain group according to the ABO system and the Rh system is genetically determined and does not change throughout life.

Also recommended

Complete blood count (without WBC and ESR)
Erythrocyte sedimentation rate (ESR)
4 mandatory tests
Screening for multiple myeloma and paraproteinemias (immunofixation of blood serum with pentavalent serum)

Who orders the examination?

Surgeon, internist, hematologist, general practitioner, transfusiologist.

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