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I only wash if I get a discrepancy I cannot resolve easily

The package insert for the reagents we use says wash a minimum of 1 time, so that's what we do with patients - 1 wash. If there is a discrepancy that isn't easily resolved we would wash the specimen 3 times - haven't had to do that in a loooong time.

As Malcolm points out, washing is not really important for ABO grouping in the modern era of tube testing. The reagents are formulated to tolerate a degree of neutralization. I assume this is true also for the reagents used in gel cards. Washing is important when using the cells in any test using antiglobulin reagents (as LIMPER55 notes). Perhaps more of a concern is that your in-house procedures should not contradict the reagent manufacturers' instructions. One could even argue that an SOP is not really required if you follow the package insert - that's your SOP! Whichever approach you take, you should definitely be following your SOP. I can see and hear the regulatory folks cringing in their seats as they read your post.

EXCEPT - for cord bloods - they ALWAYS have to be washed at least 3 times! I was just doing one and noticed that we forgot to mention them as the exception to the "rules" being discussed here. For adults - I do not wash - just make a 3% suspension in PBS from 1 drop of packed cells. I always do tell my students that if they use too many drops of packed cells, they should wash 1 time at least. For cord bloods, I make a 3% suspension and then drip that out to the test tubes (1 drop each) and then let the cell washer wash the those tubes 4 times. Very easy. (But it always requires telling the students that they must not wash the 3% suspension directly in the cell washer!!!)

The wash step used to be vital in the days when we used human-derived polyclonal ABO grouping reagents, as there were occasions recorded in the literature whereby the ABO soluble substance in some individual's serum/plasma was in sufficient amounts to adsorb the anti-A or anti-B, and thus cause either falsely weak, or even false negative reactions on some occasions, leading to ABO mismatched transfusions. The monoclonal ABO grouping reagents used now are very different, being much more avid and much more specific to the Type 2 ABO structures expressed on the red cells, and so the washing step is no longer required.

I stopped "washing cord blood samples 3 times" over 20 years ago. Routine washing of cord blood red cells is a "solution" looking for a problem. If you have documented evidence in your facility that unwashed cord red cells produce a high incidence of false-positive test results, then wash, wash, wash. Otherwise, I would wash cord red cells only when a discrepancy is detected (positive Rh control test).

I say change your SOP to match your practice, as long as it has been validated, passes daily QC and doesn't contradict manufacturers requirements. I don't know of any transfusion services that wash the cell suspensions routinely anymore.

Excellent point David. Actually, we do wash the red cells in PBS pre-warmed to 37oC several times over, if there is a cold-auto-antibody present that is interfering with the results.

Placenta accreta, in itself, is probably the reason for the C-section, and the condition being present in the first place suggests that this is not the woman's first pregnancy (although this is by no means true in all cases), and this may explain the apparent (and probable) secondary immunisation. One symptom of Placenta accreta is also PV haemorrhage and, even if this was a silent event, it would also add weight to the theory of a secondary immune response. As far as the baby is concerned, that is what I would have expected. Thanks for that gagpinks. A very interesting case. Keep us informed of any further developments, if you wouldn't mind.

Hi Sorry for late reply. Patient has known for placenta acreta so we are not sure the reason for c-section. (due to clinical condition or rising antibody level) Baby's DAT is positive (obviously ) and Hb is 175 g/L and bilirubin is elevated to 89 umol/L . Baby is on phototherapy, no blood required so far. Thanks

Certainly not Steve - 2 as a minimum!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Hi Steve, I'll give it a go anyway! Almost everyone in the world is positive for the LW(a) antigen (and a few for the LW( antigen. However, auto-anti-LW (I use the generic term, because very few have ever been differentiated into auto-anti-LWa or auto-anti-LWb) is quite a common specificity in AIHA (again, how common, I couldn't say, because most of the time, we don't bother going for the specificity, because it would make no difference to the clinical treatment of the patient), and, in some cases, the patient becomes transiently serologically LW weak or LW-. It is unclear as to whether the red cells are actually LW weak or LW-, or just that the antigen sites are blocked by the auto-antibody, but, again, so what! Anyway, as you know, anti-LW reacts very much like anti-D, except that D- red cells, like D+ red cells, are also LW+, but have weaken expression of the LW antigen. This is because the number of LW antigen sites on D- red cells (average 2835) is much less than on D+ red cells (average 4400 sites); hence it can look like anti-D. Very often, when red cells are treated with papain, the anti-LW will react equally strongly with D+ or D- red cells, BUT by IAT, the anti-LW will react much more strongly with the D+ red cells than the D- red cells (essentially, you get no visible reaction). Now then, for some reason, the LW antigen is expressed MUCH more stongly on cord red cells, again, because of the number of LW antigen sites (average 5150 for D+ cord blood cells, and 3620 for D- cord blood cells). AS you can see from these figures, the number of LW sites on a D- cord blood cells (3620) is higher than the number of sites on an adult D- red cell (2835) and, although not as high a number of sites as on an adult D+ red cell (4400), will often react visibly with an anti-LW by IAT. D- cord blood cells will not, of course, react with a true anti-D, therefore, if a group O, D-, DAT- cord blood cell reacts by IAT with an antibody that looks like an anti-D (but anti-D is unlikely, from the patient's history), then there is an excellent chance that the true specificity is anti-LW. I hope that helps?????????? :whew::whew: