Coomb's Test - Guideline for the Management of Baby with a Positive Coombs’ Test

Publication: 01/02/2011  --
Last review: 30/01/2020  
Next review: 30/01/2023  
Clinical Guideline
CURRENT 
ID: 2377 
Approved By: Trust Clinical Guidelines Group 
Copyright© Leeds Teaching Hospitals NHS Trust 2020  

 

This Clinical Guideline is intended for use by healthcare professionals within Leeds unless otherwise stated.
For healthcare professionals in other trusts, please ensure that you consult relevant local and national guidance.

Guideline for the Management of Baby with a Positive Coombs’ Test

Introduction

Coombs’ test (direct Coombs’ test [DCT] or direct antiglobulin test [DAT]) is a simple and elegant test invented by Robin Coombs, Professor of Immunology in Cambridge in 1945. 

A positive Coombs’ test means that there is an antibody attached to the baby’s red blood cells.  The antibody will have come from the maternal circulation.  In some cases the antibody will lead to fetal and neonatal haemolytic disease.

The most important cause of neonatal haemolytic disease is Rhesus D alloimmunisation.  The key to prevention of this condition is avoidance of maternal immunisation.  Mothers who are known to be Rhesus D negative are now given passive immunisation with anti-D globulin during any pregnancy.  It is normal for there to be small feto-maternal blood leak during pregnancy, and particularly during delivery.  This fetal blood may immunise the mother to Rhesus D.  Passive immunisation of the mother will remove fetal Rhesus D positive from the mother without the mother showing an active immunological response.  This management has almost eradicated the previously severe condition of Rhesus D haemolytic disease of the newborn.

However, the anti-D administered to the mother will cross the placenta and, if the fetus is Rhesus positive, small amounts will attach to the fetal red blood cells.  This does not lead to fetal haemolytic disease, but it will give a positive Coombs’ test in the newborn infant.   This can make interpretation of a positive Coombs’ test difficult. 

It follows that:

  • Most infants with a positive Coombs’ test have no risk of haemolysis as this is simply the result of passive maternal immunisation. 
  • Babies with haemolytic disease of the newborn have a positive Coombs’ test.

In the newborn baby with a positive Coombs’ test it is important to make an assessment.  Is the baby’s positive Coombs’ test simply the result of maternal passive immunisation?  Is this a baby with a positive Coombs’ test because of maternal alloimmunisation to the Rhesus D antigen, or one of the other rhesus antigens or one of the other red blood cell antigens?

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Golden rules

The baby with a positive Coombs’ test is most unlikely to have haemolytic disease and no further action is needed if all of the following apply.

  1. Mother has had anti-D antibody passive immunisation before birth.
  2. Mother has no rising titre of anti-D antibody during pregnancy.
  3. Mother has no antibody titre against other red cell antigens (eg, c, E, Kell etc)
  4. Baby is not jaundiced or has mild physiological jaundice or jaundice controlled by single phototherapy at more than 24 hours of age. [Jaundice requiring phototherapy within the first 24 hours should be assumed to be pathological and may be due to haemolysis. ]
  5. Baby is not clinically anaemic or has a normal haemoglobin on testing.

If all five rules are met then no investigation is required, reassurance can be given and we can explain that it is most unlikely but possible that jaundice will occur.  If a baby goes on to develop severe jaundice, it will be necessary to have blood tests to look for anaemia and the mother or midwife noting the jaundice should refer back to the neonatal service.

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Provenance

Record: 2377
Objective:
  • To understand the pathophysiology behind a positive Coombs test
  • To understand the mechanisms behind a positive Coombs test
  • To enable sound evaluation of the Coombs positive patient
  • To streamline ongoing investigation of the Coombs positive infant
Clinical condition:

Coombs positive jaundice

Target patient group: Newborn infants
Target professional group(s): Secondary Care Doctors
Secondary Care Nurses
Midwives
Adapted from:

Evidence base

Textbook of Neonatology, Ed Rennie and Roberton, 4th Ed.

Approved By

Trust Clinical Guidelines Group

Document history

LHP version 1.0

Related information

Not supplied

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