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Irregular agglutinins? Definition of Irregular Agglutinin Analysis

The agglutinins are antibodies, that is to say, molecules produced by the immune system to "identify" foreign agents.
The agglutinins are antibodies, that is to say, molecules produced by the immune system to "identify" foreign agents.
The term "irregular agglutinins" refers to antibodies directed against certain molecules (antigens) present on the surface of red blood cells. 
These antibodies are "irregular" because they are abnormal, with a potentially dangerous effect. 
Indeed, they may turn against the patient's own red blood cells and attack them, in some ways.
The search for irregular agglutinins (RAI) is, therefore, a necessary examination in many situations, including pregnancy, to avoid this type of complication.
Irregular agglutinins? Definition of Irregular Agglutinin Analysis

The presence of these abnormal antibodies is usually due to previous transfusion or pregnancy in women. Thus, during a transfusion or pregnancy, "foreign" blood (that of the donor or fetus) comes into contact with the blood of the individual. In response, the immune system produces antibodies against these foreign red blood cells. During a second exposure (new transfusion or new pregnancy), these antibodies may react strongly and cause the destruction of red blood cells, which may have serious clinical consequences (transfusion shock, for example).
In a pregnant woman, the presence of this type of antibody can cause, in some cases, a serious illness called the hemolytic disease of the newborn.
Irregular agglutinins may also result from autoimmunization (disruption of the immune system). It is then autoantibodies, directed against antigens of the patient himself.

Why make an assay for irregular agglutinins?

RAI aims to highlight the presence of antibodies against red blood cells.
These antibodies are of several types (depending on the molecule they are targeting). 
They are potentially dangerous in case of transfusion or pregnancy.
The RAI is therefore systematically carried out:
  • in any person likely to be transfused
  • after any transfusion (as part of hemovigilance monitoring)
  • in all pregnant women
During pregnancy, RAI is routine at least 2 times in women with no history of transfusion (before the end of the 3 rd month of pregnancy and during the 8 th and / or 9 the month). It is more common (at least 4 times) in Rh-negative women (about 15% of the population).
This examination aims to prevent transfusional or fœto-maternal accidents ( severe anemia, hemorrhages, jaundice).
For example, such accidents can occur when a woman is Rh negative (negative blood group) and is pregnant with a Rh positive male. During the first pregnancy, the blood of the fetus (if it is Rh +, too), does not come into contact with that of the mother, so there is no problem. On the other hand, during delivery, the two types of blood come in contact and the mother will produce positive anti-Rh antibodies. This contact can also take place in case of miscarriage or abortion.
During a second pregnancy, these antibodies may cause a miscarriage (if the fetus is Rh + again), or a hemolytic disease of the newborn, that is to say, a massive destruction of red blood cells of the baby. To prevent this complication, it is sufficient, at each delivery, to inject the mother with an anti-Rh serum (or anti-D), which will destroy the few red blood cells of the baby that have passed through the maternal circulation and prevent immunization.

Procedure for the analysis of irregular agglutinins and results

The examination is carried out by a simple  blood test, in a laboratory of medical analyzes. The patient's blood is brought into contact with a range of donor cells (which represent the diversity of antigens against which irregular agglutinins may form). If irregular agglutinins, they will react in the presence of these cells.

What results are expected by looking for irregular agglutinins?

The examination is either negative or positive, showing or not the presence of irregular agglutinins in the blood.
If the screening is positive, it will be necessary to determine precisely which antibodies it is (in order to know exactly against which molecule they can react).
In case of a subsequent transfusion, this allows the selection of compatible blood for the patient.
During pregnancy, the presence of irregular agglutinins is not necessarily dangerous. Very often, these antibodies do not present any risk for the child (they are not very "aggressive" or the fetus can be compatible).
The good development of the fetus will, however, be strictly controlled.
Agglutinins called "anti-D" (anti-RH1, but also anti-RH4 and anti-KEL1), in particular, require regular monitoring and dosing (at least once a month until delivery and even all 8 to 15 days in the third quarter). The doctor will explain the risks and conditions of pre- and postnatal follow-up.