Antibody screen status change in OB patients

[Deny Morlino]

Looking for a quick bit of information. How often do we see a change from a negative antibody screen at the prenatal workup to a positive antibody screen at delivery (excluding the obvious of RhIg administration causing a change in the Anti-D)? Anyone with some sort of guestimate? I do not recall many changes, but we do not routinely perform a type and screen at admission. Thanks in advance for the replies.

[Malcolm Needs ☆]

Can't help you here Deny. WE only ever see them after a hospital has seen them.

That having been said, only today we had a sample at partum from a lady we had been following throughout her pregnancy with an anti-E only, who suddenly popped an anti-c (quite strong too) at delivery.

[Yanxia]

What about medicine or bacterium infection?

[John C. Staley]

Deny, if I recall correctly that was a very rare occurence. It did happen but I would be surprised if it were more than once per year, if that. I was at 2 of the larger facilities in the area, 250 and 300 beds, and between them they perform most of the prenatal work ups and deliveries in the area. I can't guess at how many deliveries but I'm certain they numbered in the hundreds/year. I do remember one anti-c that was pretty bad for the baby but I don't recall any others specifically. I was 20 years in the 1st hospital and 15 in the second. During that time policies changed over the years from T&S for every pregnant woman walking through the door to just those with no history or Rh Neg or as ordered. Hopefully that gives you a little idea of my reference points for my first statement.

:coffeecup

[adiescast]

I don't have numbers, but I would also say that it is very rare. It is more common (although still rare) for a woman with one antibody to demonstrate a second antibody (as Malcolm has attested) than for a negative to go to positive (barring RhIg administration).

[Mabel Adams]

I saw one anti-D develop during a pregnancy due to repeated *** bleeding and leaving the ED against medical advice before getting RhIG. She had an affected baby I believe (she had to deliver at the bigger hospital with a NICU so no details available to me). I saw one or two others develop additional antibodies but none caused the baby significant problems. I spent 27 years in a community that delivered about a thousand babies per year and the past 3 years where we deliver 2000 per year. I think John Judd has said that generally if an antibody isn't detectable early in pregnancy, it is unlikely to cause severe problems to the infant that require early delivery or other intervention before birth. Not to say it can't happen.

[Deny Morlino]

Many thanks for the replies thus far.

[Auntie-D]

I've seen K, C and c that haven't shown up at 28 weeks but were present at delivery. Fortunately everywhere I have worked so far tests mothers at delivery, if they weren't tested it wouldn't have been known until the next pregnancy or during a requirement for blood. Better to be prepared IMO, especially since some antibodies can have the titre fall to ur detectable levels over time. Catch them while you can

[Deny Morlino]

Good points Auntie-D. Thanks

[Brenda K Hutson]

Can't give you a number, but a lot of experience tells me it is very infrequent. Most instances have been women without prenatal testing (which does not include the population you asked about), and some patients who had erroneous testing by outside Labs (does happen; not sure of frequency since not all patients have a Type and Screen ordered when delivering).

Brenda Hutson

[AMcCord]

We only do OB antibody screens for C- sections, patients with no type (very uncommon) and patients who need blood (also pretty uncommon). We delivery 750-800 babies per year (guesstimate) and I've been here 31 years. In that time, in that patient group, I can remember only 3 patients who developed an antibody during pregnancy. I think they were all directed against Rh antigens...I'm thinking one anti-D and it seems like the others were either anti-E or anti-c.

Up until the last few years, we have done almost all the Prenatals for OBs delivering here. Even when I think about patients with previously negative Prenatal antibody screens who showed a positive screen with the next pregnancy, the number is quite small.

[rravkin@aol.com]

Denny,

Much of any adversity that occurs in our practice is of such a low percentage, however it is our practice that incurrs this low percentage. Performing a type and screen as part of the prenatal workup is ultimately beneficial for the patient and the neonate. It is just good practice that would better prepare us if the screen does turn positive during the course of pregnancy. If we did not do the initial screen would we know if the positive was new and/or potentially gestational in origin? Are you questioning this practice as a cost cutting messure?

[Rh-fan]

A few years ago a large study is performd to follow women with klin relevant antibodies during pregnancy (OPZI study). During this study we also looked foor childeren with severe HDN (need of a (exchange)transfusion) while the antibdy screening at week 12 was negative. There were 6 of 7 childeren with severe HDN (even one with kern-ictarus) all were anti c antibodies. This is why we (the netherlands) started in july 2011 to type women at weak 12 for the presence of the c antigen (beside ABO RhD and antibody screening) and repeat the antibody screening for those that are c negatieve at weak 27 (just as the RhD neg women). We expect to find more than 6 women per year because we have only looked at those who became sick.

Peter

[Mabel Adams]

Peter, is the frequency of the c antigen about 80% in your population as it is in ours? Also, what was the 7th antibody specificity that caused severe HDN? How many total pregnant women with negative screens at 12 weeks were studied to find the 7 cases of severe HDN?

[Rh-fan]

Mabel,

Yes it is 80-82% in our population. Beside the anti c we also found a few anti E (mostly together). But for more details I have to look into the publication. I will try to find it and send you a copy.

Peter

[Malcolm Needs ☆]

Hi Peter,

Would you mind citing the reference here please too?

Malcolm

[Rh-fan]

For mabel and Malcolm (and others who are interested).

Transfusion 2008; 48 (5): 941-952

This is the tekst I was refering to

page 948-949

Severe HDFN in screen-undetected cases

The coverage validation study identified eight cases of

severe HDFN, all with a negative screen at the first

trimester; seven of eight infants needed an exchange

transfusion because of anti-c (n = 3), anti-c and anti-E

(n = 2), or anti-E (n = 2), respectively (Table 4). One of the

children (anti-c plus anti-E) suffered from kernicterus

with a maximum bilirubin level of 1109 mmol per L and

showed permanent severe brain damage at 1 year.

Another child (anti-c) had an intracerebral bleeding,

caused by asphyxia, possibly related to the severe prenatal

anemia (Hb 2.4 mmol/L = 3.8 g/dL). At 1 year, the prognosis

was still unclear. One child only needed a top-up transfusion

because of anti-Miltenberger, a low-incidence

antigen. In this child other unrelated morbidity contributed

to the observed anemia. The prevalence of severe

HDFN with negative antibody screens was 2 in 100,000,

leading to a total prevalence of 9 in 100,000 (Table 4).

[ATTACH]596[/ATTACH]

As you can see mostly anti c(+E), some anti E and one Miltenberger (you never will find during screening.

(I hope the attachment worked)

Peter

[Malcolm Needs ☆]

I do so agree with you Peter that anti-c is a very dangerous antibody in pregnancy. I attach part of a document that is in the Library of this site in which I explain why I think that ALL c- females of child-bearing potential should be transfused with c- blood.[ATTACH]597[/ATTACH]

[Mabel Adams]

Maybe donor centers can start DNA testing of donors for c so all Rh pos units could come labeled as to their c type.

[Rh-fan]

Maybe donor centers can start DNA testing of donors for c so all Rh pos units could come labeled as to their c type.

What is wrong with serology? A bottle of anti c is not that expensive, and it is very easy. Also for card methodes there are cards (Diamed/Biorad).

If the donor centers start with DNA typing it is cheaper to test al the antigens (or genes).

In the Netherlands we have one blood supplier and they perform an Rh fenotyping on all donations.

[AMcCord]

This conversation about c antigen and OB patients is interesting because we used to have a policy of typing all OBs for the c antigen. The pathologist who was here when I started working had done a stint with the US Army and it was apparently Army policy (or at least at the facilities where he worked) that all women 'of child bearing age' receive c negative blood if they lacked the antigen. He also required that we type for c antigen on all prenatal panels. We went through buckets of anti-c antisera. When antisera skyrocketed in price, we stopped typing OBs routinely, but did continue the practice when transfusing 'women of childbearing age'. When the pathologist retired, that policy retired with him. I would say that over 2/3 of the antibodies we identify with prenatal panels are anti-E and we do type for c antigen in those cases.

The last case of HDN that we had (within the last 6 months) was due to anti-c, which was ID'd on the prenatal panel. That's the only case of HDN due to anti-c that I've seen in 30+ years, fortunately. The patient was followed with titers and we made sure that we had c negative red cells on hand for the last month of the pregnancy, knowing that the physician would never think to let us know when the patient's deliver was planned. (Why plan ahead if you can give the Blood Bank a heart attack asking for antigen typed blood RIGHT NOW!?) We did transfuse the baby, so our precautions served us well.

[Rh-fan]

(Why plan ahead if you can give the Blood Bank a heart attack asking for antigen typed blood RIGHT NOW!?)

[Malcolm Needs ☆]

(Why plan ahead if you can give the Blood Bank a heart attack asking for antigen typed blood RIGHT NOW!?)

We even see this with antibodies to a HFA, just wait till they delivere (mostly in the weekend) and then call the bloodbank/reference lab. "We want blood now".

[Deny Morlino]

Sorry for the delay in reply ( first vacation in almost 2 years and was avoiding anything "work" related). At present we perform an antibody screen at the point of prenatal workup (usually 16-20 weeks). If the patient is Rh negative, we also perform an antibody screen when the patient presents with an order for RhIg (28 weeks). The question I was lookin for an answer to was the frequency we see a change from a negative antibody screen during the course of the pregnancy to a positive at term. From the replies there appears to be a very low occurrance of a change to positive, but the change appears to have a higher frequency of being a c antibody than anything else.

Peter, thanks for the reference and the discussion on the article in Transfusion. As has been stated, this is an interesting topic!!

[Mabel Adams]

Although we have not had a policy regarding little c for OB patients, we do give c neg blood to c neg patients that have made anti-E. Although some will argue that we shouldn't use the precious resource of c neg units on a patient that does not have anti-c it does preserve the possibility of giving them blood in an emergency that is more likely to be compatible. We are the only hospital in about a 150 mile radius that does antibody IDs and can antigen type units so this not only could help us in an emergency but also the other 4 surrounding hospitals that transfuse an average of 11 to 75 units of RBCs per month. Do the UK and The Netherlands have hospitals this small? I know your population densities are a bit different than here.