Hi

I took care of a baby who's mother is B+ and baby is A+ with a DAST/Coombs+. The DAT was sent inarventently  since we only sent DAT in mother's with blood tupe O or rh negative. I was surprised to see this results since I have always understand that ABO incompatibility  that cause significant hemolysis is only produced when mother is O and baby is A or B group. The reason for this ABO incompatibility set is not too clear. I understand its because when mama is O and baby is A or B; IgG antibodies casn be produced during gestation that will cross the placentas . Unlike when mama is A and baby is B or mama is B and baby is A only igM antibodies are produce yhjat will not cross the placenta. I am not sure why this is  produced this way??

Any input or insights will be apreciated

 

There can be minor antibodies present such as Kell and Duffy.  

This is also my first thought, that the DAT+ is not related to the AB0 type but another antigen. 

No other antibodies were present in mother's circulation.

If mother's indirect coombs is negative , then maybe false positive result ?

DCT IS NOT SPECIFIC neither 100% sensitive 

It can also occur in such setting but much less likely. 

According to Avery's text.  It is possible for Group A or B infants born to incompatable A or B mothers will have a small chance of a positive combs test, though unlikely to cause significant hyperbilirubinemia. 

"Infants born of ABO-incompatible mother–infant pairs who have a negative direct Coombs test appear to be at no greater risk for developing hyperbilirubinemia than their ABO-compatible counterparts (Ozolek et al., 1994), and the development of significant hyperbilirubinemia in such neonates should prompt an evaluation for a cause other than isoimmunization (Herschel et al., 2002). Similarly, group A or B infants born to incompatible group B or A mothers are not likely to manifest symptomatic ABO hemolytic disease, and less than 1% will have a positive direct Coombs test (Ozolek et al., 1994)."

First of all this not ABO incompatibility 

Think of Minor  blood groups mismatch and look for active hemolytic state (may be Reti & PS ) may help. THANKS