Rh Antibody Titre
Rh Antibody Titre
Apart from the blood group, A, B, O and AB, we have another factor that differentiates our blood, which is the presence of a protein called as the rhesus factor (Rh). Presence of the rhesus protein implies you are rhesus positive (Rh positive) and its absence means that you are rhesus negative (Rh negative). If Rh positive blood is introduced in a person with Rh negative blood group, the body of the person with Rh negative blood group would produce antibodies against this protein. This scenario may arise when a pregnant woman with Rh negative blood group has a foetus with Rh positive blood group. Usually the blood from the foetus does not mix with the mother’s blood, but due to certain situations like miscarriage, bleeding during pregnancy etc., there may be mixing of the blood, resulting in producing antibodies against the rhesus protein, which may cause complications for the foetus during the next pregnancy, especially if the next foetus is also Rh positive. These antibodies can cross the placenta and may damage the blood cells of the baby, causing a fatal form of anemia. The Rh antibody titre test is done to monitor the level of this antibody, called as anti Rh immune globulin, so that preventive measures can be taken for the wellbeing of both mother and child
What is the Rh Antibody Titre Test Used For?
The Rh Antibody titre test is used for determining the level of anti-rhesus antibodies in the mother’s blood, especially when the mother is Rh negative and her baby is Rh positive
Rh Antibody titre test
Preparation for Test
Before the test, let your general physician know of any medication, supplements or treatments that you are consuming. If Rh immune globulin has been administered please let your physician know, as it may interfere with the results. Usually no preparations are required. Blood sample would be taken from the mother’s vein in the arm
Interpretation of Test Results
In this test, the serum from the blood sample from the mother is diluted serially and then uniform amounts of O positive (O blood group with rhesus positive) is added. These dilutions would be 1: 2, then 1: 4, 1:8 and so on. If anti-rhesus antibodies are present in the mother’s serum, it would bind to the rhesus factor from the O positive blood added. After that Coomb’s reagent is added to all the dilutions. If there is a clumping of the blood cells, it would confirm the presence of anti-rhesus antibodies in the serum of the mother’s blood sample.
Titre is expressed as the inverse of the highest dilution for which clumping of blood cells was observed. If there was clumping of blood sample in the dilution with say 1:2, then the titre would be reported as 2. This would indicate that the result of the test is positive. If there was no visible clumping of the cells in the test for any of the dilutions, then the test is negative, and there are no antibodies against the rhesus protein in the mother’s blood.
An antibody titre of less than 16 is considered safe, and these levels would be monitored for the rest of the course of the pregnancy. If clumping of the blood cells are observed in very diluted serum samples, it would mean that the level of the antibody against rhesus protein is high and can be dangerous for the next pregnancy
FAQs
How is the sample collected for the Rh Antibody titre test?
A blood sample is collected from a vein in your arm
What is the turnaround time (TAT) for Rh Antibody titre test?
The tests results should come within 1-4 days after the sample is taken. This time would depend on the diagnostic laboratory that has taken the sample for analysis
What should we do if we get a positive titre test?
In case, the titre test is positive, depending on the level of antibodies already present in the mother’s blood, a shot of Rh immune globulin may be given in regular intervals to the mother so that the foetus would not be harmed
What happens to the child if the titre is more than 16 and the child is Rh positive?
The foetus would be at a risk of hemolytic disease of the foetus and newborn (HDFN). In this disease, the red blood cells of the foetus would degrade at a rapid rate due to the presence of antibodies in the mother’s body, causing developmental delays in the foetus and if uncontrolled, may cause death of the foetus
How to prevent this situation?
If the mother’s blood group is Rh negative, and the first child is Rh positive, the mother must undergo a blood test called antibody screen to check the presence of anti Rh antibodies at regular intervals during the first pregnancy and also after childbirth. If the anti-rhesus antibodies have not been produced, then Rh Immune globulin shot would be given so that these antibodies are not produced in the body during and after pregnancy
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