Mabel Adams

I remember being told that the entire fetal blood volume would not exceed the 30 mls covered by one dose of RHIG until after 20 weeks gestation. However, since then I have heard of cases with chronic fetal-maternal bleeds where maybe more than that could (rarely) accumulate over time as the baby makes more red cells. That would probably mean a FMH could conceivably be that big earlier than 20 weeks. Of course twin pregnancies would change the value too.

Is there any data on the effectiveness of two people doing the ID? I seem to remember reading once that it didn't improve much because each person figured the other one was paying attention and taking responsibility. Like everything, I suppose it is in the details: understanding of the need, training, adherence to the intent of the policy and reduction of factors increasing the odds of human error (fatigue, distraction). Get those right and any policy will work better.

Because the package insert says you should. However, I recall a lengthy debate on the AABB forums several years ago which revealed that many of us can't achieve a time-frame much better than 24 hours. Considering the rarity of RhIG failure, I doubt if we are causing much of a problem for our patients if it takes a few extra hours. Here's my logic for why it doesn't really matter so much: The claim is that ABO incompatible fetal cells will be removed from the mother's circulation fairly quickly so we need to collect a sample before those fetal cells are removed or we won't get an accurate count of the amount of fetal bleed. In the days before RhIG, it was observed that Rh neg moms whose babies were ABO incompatible with them were less likely to become sensitized to D. The theory I heard was that the ABO incompatible cells were removed by intravascular hemolysis so were never presented to the immune system like ABO compatible fetal cells would be when they are removed by the spleen. Seems to me the fetal cells the rosette testing package inserts are so worried about us detecting are not likely to cause sensitization anyway. Someone feel free to correct me if I am wrong.

Can someone explain how prozone would interfere with a direct coombs? It seems like the Fc portion of the antibody attached to the cells would still be available for the anti-IgG to attach to even if all the antigen sites on the red cell were full due to the high titer of the antibody. Also, I have read and done some small studies myself that most non-O babies of O moms have mom's ABO antibodies in their plasma/serum and on their red cells even if they have no symptoms of HDN and have a negative DAT. John Judd said that looking for the ABO antibody in cord blood was really only diagnostic if the expected one was missing. Then you needed to look elsewhere for the cause. If you find ABO antibodies in the cord blood, you don't know for sure whether it is the cause or an innocent bystander.

Happy New Year Yanxia!

http://en.wikipedia.org/wiki/Human_blood_group_systems might help.

I hope to revise our protocol soon to better capture symptoms of TRALI. We will have an ongoing need to educate docs, nurses and lab folks also. The only suspected cases we have had, the doc did not see any reason to report it to the BB although he told the family! Fortunately, they didn't really fit TRALI, but still...

We attach the IT card from Meditech to the unit and only occasionally hear of a nurse taking it off. We have been on MT about a year and had a removable transfusion slip (along with a manually completed Hollister label) on the units before that which we no longer have. Maybe you need some bright stickers on the IT card that say "tag must remaiin attached to unit throughout transfusion!" After a few years maybe you wouldn't need them anymore. Also, maybe there is a reason they remove it. Does it look like it has spaces for them to fill out? Is it in their way? Do you have traveling nurses that do it mostly? Time for "root cause analysis" to the rescue!

Well, John, that explains a lot. I didn't realize there was an automated survey. Thanks.

I won't really try to change your mind because I think a second specimen is better too. However, the statistics on mistransfusion show that errors in the BB are not a miniscule percentage. Maybe a 20% increment of improvement is worth something--especially when retyping the sample is so easy. Of course, at our facility, we wouldn't have the luxury of a second tech to do it most of the time. Getting that second specimen introduces some big issues for us--especially since one of our hospitals is a 15 min. drive away.

I wonder if there have been any studies done, or if these policies are just what made someone feel better about it.

I wonder if leuko-reduction before irradiation might make irradiation more effective since there are fewer wbcs present to zap. Hmm. Might be irrelevant, but just curious. Didn't they try leukoreduction in Japan and had to go to irradiation of all units because they have such a genetically homogenous society some patients that were not immunosuppressed were getting GVHD from unrelated donors?

We used to scan units into the computer for testing, but since we switched to Meditech, we don't do it this way. As you know Meditech isn't user-friendly for antigen typing. We have a paper log. We put a barcode unit sticker on the log. I made a laminated template to go over the log with see-through and/or open spaces for the current line to keep our eyes on the right line. We can then scan the unit number right through the template into Unit Edit to add the ag typing. Then we mark through the template onto the log to document that we have entered that one and move down to the next line. It is not foolproof. We could put the wrong sticker on the log initially or crossmatch the wrong unit. In the latter case, Meditech should flag that the unit isn't antigen typed so the tech should know to double-check. The only problem is that Meditech is known for tossing up messages when you don't expect them so the techs don't always trust it to be right. I would be interested in any solutions for places that only have one tech and an MLT on at night & almost never more than one tech in BB. Rechecks by second techs are pretty tough in that circumstance. Sometimes they assume that the original must be right and don't check very hard or the first person assumes that the second will catch any mistakes. I think a good deal of fear about antigen typing is a healthy thing.

If you look at the CAP survey results where they report the method used, you see vastly more gel users than solid phase. It will be interesting to see if the levels change due to introduction of the Echo.

We don't use the word Kalium that I know of here. Is that Potassium, (chemical symbol is K)? I see that wikipedia says that Kalium is the Latin word for Potassium--that must be where the K came from in the symbol. Another educational moment!

Our OB dept. was getting annoyed with the delay of identifying the anti-D in pos postnatal screens. Plus it was more costly. Besides the same action was going to be taken (give RhIG) regardless of the result fo the screen. If some other antibody was going to be found, the baby would probably have a pos DAT causing a workup that ID'd it. If not, the mom probably wasn't going to decide about getting pregnant again, based on the fact that she has an anti-K. It would be dealt with in the next pregnancy, if there is one.

Pardon my ignorance, but what is a chown tube?

Only IgG antibodies cross the placenta. Only certain classes of IgG can fix complement. Certain IgG classes cross the placenta better than others. I know it is in Issitt, but I don't have the book at home with me. Then there is the fact of a baby's complement levels and if they even work like an adult's. Even if it is theoretically possible, I think the experts agree that it isn't necessary to look for complement-only antibodies in cord blood.

What can we do to make our special antisera go further? I believe there are methods for using gel cards and small volumes of antisera. Anyone have a method they would care to share? I really like the monoclonal K and Jka antisera that only take 5 min at RT, but could probably stand to spin them in gel for 10 min. if it is enough cheaper. Is Ortho marketing special typing cards with reagent already in the cards? I never see an Ortho rep so don't get updates on their products.

Re: freezing your old antisera. I believe it was the late John Case, previous guru of Gamma, that once said on the AABB forums that it was probably better to just refrigerate old antisera rather than freeze it. I have been doing that for years now with results about as good as when I froze it. Obviously this expired stuff isn't for routine use.

Did you test the eluate against A cells? If there happened to be any anti-A in it, this would react with the father's cells and could mislead you. If a baby needs to be delivered early due to risks of HDN, then a Caesarean might be necessary, but unless there are other reasons to do a Caesarean, a vaginal delivery should be fine. If you needed to do an exchange transfusion, donor blood should be ABO and Rh compatible with both the mother and the baby and compatible with any other antibodies the mother has--at least if you are going to do the crossmatch using the mother's serum. You could use B neg or O neg units in the case you described.

As I understand it, even one viable lymphocyte could grow into a clone that could cause GVHD. So even after leuko-reduction, residual lymphocytes must be irradiated to make them incapable of dividing into more cells.

Do you find gel DATs to be a lot more sensitive than tube? We certainly pick up a lot of auto controls in manual gel but the sample tested by tube DAT (IgG) is negative. I would not be thrilled to do eluates on all those that are recently transfused unless it was going to provide me some pretty meaningful information. This is why I have hesitated to use gel IgG cards for DATs.

Anna, I think the language issue is a nuance. We might say we did "doubling dilutions" but I hadn't heard the verb form that I can think of--it seemed an understandable extension, so I knew what you meant after a second's thought. Of course, I am an old blood banker who was taught things like ASO titers in school. One of the nice things about this forum is that it is open to us as well as generalists and those from different backgrounds. I enjoy your unique perspective.

I wonder if so much testing for a baby that isn't even yellow can be a justified use of resources. I think more limited testing was recommended in the Perinatal Guidelines book that AABB put out.