Rh Antibody Titre / Anti-D Titre Test

The Rh Antibody Titre (Anti-D Titre Test) measures the level of anti-D antibodies in the blood. These antibodies are produced when an Rh-negative (Rh−) person is exposed to Rh-positive (Rh+) red blood cells. This test is particularly important during pregnancy and blood transfusions to prevent hemolytic disease of the newborn (HDN) and transfusion reactions.

Why is the Test Done?

✅ During Pregnancy (for Rh-negative mothers) – To check if the mother has developed anti-D antibodies against an Rh-positive baby’s blood.
✅ Before Blood Transfusions – To ensure Rh compatibility between donor and recipient.
✅ After Miscarriage, Abortion, or Ectopic Pregnancy – To detect Rh sensitization.
✅ After Trauma During Pregnancy – If there is a risk of fetal-maternal bleeding (e.g., car accident).

How is the Test Done?

1. Blood Sample Collection:

   • A blood sample is taken from a vein.
   • The test is performed using Indirect Coombs Test (ICT).

2. Measuring the Antibody Levels:

   • Results are given as a titre (1:2, 1:4, 1:8, etc.), indicating the dilution at which antibodies are still detectable.

Interpreting the Results

📌 Note:

• A negative result means no Rh sensitization has occurred.
• A rising titre suggests Rh sensitization, which may cause HDN in the baby.
• If titre is >1:16, fetal monitoring and further testing (e.g., Doppler ultrasound of the middle cerebral artery) are needed.

Next Steps Based on Results

🔬 Additional Tests May Be Ordered:

• Indirect Coombs Test (ICT) – Confirms Rh sensitization.
• Fetal Doppler Ultrasound – Checks for signs of fetal anemia.
• Amniocentesis – Measures bilirubin levels in the amniotic fluid.

💊 Management & Treatment:

• If Rh-negative mother is NOT sensitized:
  • Rh immunoglobulin (RhoGAM) injection at 28 weeks and within 72 hours after delivery if the baby is Rh-positive.
• If Rh-negative mother is sensitized (Positive Anti-D Titre):
  • Close fetal monitoring for signs of hemolytic disease.
  • In severe cases, intrauterine blood transfusion may be needed.