RhoGAM and Coombs

KLKRN, RN · Feb 28, 2008

When I was in nursing school, the anatomy teacher incorrectly marked an answer of mine wrong. I took the book up to him and showed him why I answered the way I did. He gave me credit for the question.

I asked him if he would give everyone who missed it credit, and he said, "only if they show me why they answered the way they did."

My point is this: find what you can on this, either here (sorry, I don't know the answer) or Google it. If you feel your answer is correct, and the instructor disagrees, you can at least back up your answer.

It's always best to know why the answer is what it is.

Try this link:http://en.wikipedia.org/wiki/Coombs_test

Good luck.

morte, LPN, LVN · Feb 28, 2008

hmmm google is our friend, and if it is on the boards, THEY wont throw it out......please take care

randomramblings · Feb 28, 2008

I'm a nursing student and we just took our OB final this morning. There was a question on the test that I'm confused by and I was hoping someone might be able to explain.
Let me preface by saying that when we covered this material, we ran out of time and so we never had lecture on this and we were told that it wouldn't be on the test. It wasn't on THAT test, but it showed up on the final. I guessed, but looking at the book and the notes, I'm not sure what the right answer is.
The question had to do with when to give RhoGam. Two of the four answers were obviously wrong. The other two were: "if both direct and indirect Coombs tests were positive" and "if both indirect and direct Coombs tests were negative."
I guessed both positive (seemed logical in that we hadn't talked about it and since we were told it wouldn't be on the test, I didn't even read about it!). Afterwords, a classmate of mine who works as a tech in OB said that was right, but when I looked at the Powerpoint for that lecture, it says you give it if they're both negative. The book only mentions it in one sentance and it's unclear.
So, which is it? I've read a lot about Coombs testing online and it seems to me that it would be if they were both positive you'd give the RhoGam, but the Powerpoint specifically days to do it if they're both negative. Can someone tell me which is right and explain why?
I'm hoping that they'll throw the question out since they did say it wouldn't be on the test, but I'd still like to know for myself.
Thanks!
Bryan

There's a difference between blood type (pos or neg) and Coombs. A coombs tests whether blood you've been exposed to is incompatible with yours. If you've received a blood transfusion or been pregnant and therefore exposed to the baby's blood cells, a coombs will be positive if your body's attacking the foreign blood cells, basically.

A lot of providers will give rhogam to an Rh negative mother regardless of whether the baby's blood type is positive or negative, just to be on the safe side. If not, a positive direct coombs on the baby (which is the test they usually do) is an indication of an incompatibility between mom and baby's blood, so they'll give mom rhogam if she hasn't already received it and will monitor the baby for potential complications.

If the coombs testing you're referring to is a test on the mother, though, they should give it if they're positive, because it means the mother has been exposed to blood it's incompatible with, meaning her antibodies (if they get into her baby's blood steam) could attack the baby's blood.

I haven't really heard of them doing any coombs tests on the mothers, though... at least not in the normal course of things. I'm surprised it was on your test!

Kelly

NeuroNP · Feb 28, 2008

There's a difference between blood type (pos or neg) and Coombs. A coombs tests whether blood you've been exposed to is incompatible with yours. If you've received a blood transfusion or been pregnant and therefore exposed to the baby's blood cells, a coombs will be positive if your body's attacking the foreign blood cells, basically.
A lot of providers will give rhogam to an Rh negative mother regardless of whether the baby's blood type is positive or negative, just to be on the safe side. If not, a positive direct coombs on the baby (which is the test they usually do) is an indication of an incompatibility between mom and baby's blood, so they'll give mom rhogam if she hasn't already received it and will monitor the baby for potential complications.
If the coombs testing you're referring to is a test on the mother, though, they should give it if they're positive, because it means the mother has been exposed to blood it's incompatible with, meaning her antibodies (if they get into her baby's blood steam) could attack the baby's blood.
I haven't really heard of them doing any coombs tests on the mothers, though... at least not in the normal course of things. I'm surprised it was on your test!
Kelly

That's what I was thinking. So, if the Coombs is positive, it means there has been exposure and you should get RhoGAM. I couldn't for the life of me figure out why you would give RhoGAM for a negative test. But, I just looked again and there it is in the Powerpoint, negative. Like I said, I'm hoping they'll throw it out, but if not, I may need to go argue.

Jolie, BSN · Feb 28, 2008

A positive indirect coombs test indicates that the mother has already produced antibodies to fetal blood, in which case Rhogam will not be effective and should not be administered.

http://books.google.com/books?id=yJf4e_GVr0gC&pg=RA1-PA442&lpg=RA1-PA442&dq=direct+coombs+test+and+rhogam&source=web&ots=SUyEhYvzVx&sig=foXiHKQckb6KB3bHBe4GL7oq3Gg&hl=en#PRA1-PA442,M1

randomramblings · Feb 28, 2008

Ah! I was just coming back to write that I've worked post-partum/maternity, not prenatal, so I wasn't 100% sure about the positive coombs in moms. Thank you for clarifying!

So if I, having 0 neg blood, have a baby who's Rh positive and I develop antibodies, they won't give me rhogam even for subsequent pregnancies?

NeuroNP · Feb 28, 2008

A positive indirect coombs test indicates that the mother has already produced antibodies to fetal blood, in which case Rhogam will not be effective and should not be administered.
http://books.google.com/books?id=yJf4e_GVr0gC&pg=RA1-PA442&lpg=RA1-PA442&dq=direct+coombs+test+and+rhogam&source=web&ots=SUyEhYvzVx&sig=foXiHKQckb6KB3bHBe4GL7oq3Gg&hl=en#PRA1-PA442,M1

Well, that was the one thing I thought about. The only rationale I could think of for giving it with a negative text was that if it was positive it was too late.

Elvish, BSN, DNP, RN, NP · Feb 29, 2008

So if I, having 0 neg blood, have a baby who's Rh positive and I develop antibodies, they won't give me rhogam even for subsequent pregnancies?

If you're Oneg, you'll probably get it around 28 weeks anyway, regardless.

randomramblings · Feb 29, 2008

So then, they DO give it to Rh neg moms regardless of positive or negative coombs? I knew that in practice, most providers give it to their Rh neg moms regardless of the baby's blood type or coombs result.

I didn't realize coombs testing on pregnant women was routine. So I assume that it's not indicated if coombs is positive, but it's also not contraindicated?

Or is this just all academic with no real bearing on actual practice (and therefore confusing to this nurse)? :)

Jolie, BSN · Mar 1, 2008

So then, they DO give it to Rh neg moms regardless of positive or negative coombs?

To my knowledge, no. It is like closing the barn door after the horse gets out. Rhogam prevents the production of antibodies by RH- mothers who have been exposed to Rh+ fetal blood. In the case of a mother whose indirect coombs is positive, the antibodies are already circulating freely in her bloodstream, and Rhogam is ineffective. There is no benefit to exposing mother to the potential risks and side-effects of the drug.

This is a fairly rare occurance, in my experience. Most Rh negative mothers are given Rhogam prophylactically upon miscarriage, abortion, any procedure that may potentially result in mixing of fetal and maternal blood (such as amniocentesis) or at 28 weeks gestation of pregnancy, making it unlikely that an Rh negative mom will develop sensitization. So a mother with a positive indirect coombs test is a rarity. The article I linked in my earlier post indicates what is done in that case. You can also "google" Rhogam for more information.

jhhrn68 · Mar 1, 2008

Here is all I know about it. A pregnant woman who is Rh negative gets Rhogam during her pregnancy. After birth, if the baby is Rh neg. also, we don't give Rhogam, but if the baby is positive, we do.