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exlimey

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Everything posted by exlimey

  1. Actually, I'm not suggesting that replacement of the batteries is cause to re-qualify a timer. Accuracy of most timers is not affected by battery replacement because there is no actual CALIBRATION, i.e., no adjustment process. Typically, today's timers are CERTIFIED - their accuracy is verified against a standard. That accuracy is independent of the batteries. But, I do agree that a broken/unreadable timer is the ultimate expression of "inaccurate".
  2. Perhaps the real question is: Do you (or the supplier/certifier) actually CALIBRATE them ? That is, can the reading be adjusted in any way ? If the timer differs greatly from the "Standard", can it be tweaked into range ? Most simple electronic (battery-powered) timers are not adjustable. I'm not even sure that the official certifiers (the ones providing the certificates) are able to adjust the cheap and cheerful electronic timers. The electronics are so reliable (and cheap) these days that it's rare to find an inaccurate timer. The ones with unacceptable performance are probably just discarded. So, back the the main issue. If the time IS calibrated and the removal of the batteries nullifies that calibration, i.e., the timer loses its mind, then YES, the timer will need recalibration upon battery replacement. But, see above, I suspect not.
  3. Tests on the adsorbed serum (with ZZAP-treated cells) give confidence that the are no underlying alloantibodies to common antigens. However, the use of allogeneic cells risks removal of a cold-reactive alloantibody to a high incidence antigen, e.g. anti-Vel, -PP1pK. A low risk, but still concerning. Does you facility also test the ZZAP-treated patient cells (now presumably DAT-negative) back against the patient's own serum ? This is ultimate proof that the cold-reactive antibody is an AUTOantibody and adds more confidence in the results of the adsorption with allogenic cells. I may be opening a can of worms here, but.....I question the use of ZZAP in this scenario. In this case, the adsorption used (presumably DAT-negative) allogenic cells. ZZAP was not required to "reduce the DAT and enhance antibody uptake" - which is a true statement about performing AUTOadsorptions with DAT-positive cells. I appreciate that the enzyme in ZZAP enhances the efficiency of the adsorption, but the DTT component is not necessary for most alloadsorptions, and can actually confuse the users. I suspect the answer/policy is related to ZZAP being commercially available, rather than in a well-founded technical reason.
  4. Arguably the initial ABO discrepancy is proof of the presence of a cold-reactive antibody. If the DAT was positive, how do you determine that the autocontrol is valid ? Surely its just the same DAT-positive cells reacting with the antiglobulin reagent, or were the patient's cells treated to render them DAT-negative prior to testing ? Were the "zzap'd cells" autologous ?
  5. Especially if the beast in question is largely IgM.
  6. That's an excellent point. It always struck me as slightly odd that such critical testing is done by "drops" - a potentially highly variable volume. One certainly wouldn't see an HIV test kit give instructions like "Dispense two drops". Goes to show that the standard serological (tube) test is extremely tolerant of variation.
  7. Wow. I perfectly understand the science, but that is an awful thing to put in a Directions for Use. A savvy Inspector could throw serious doubt on any tests performed using the supplied dropper. And why provide a dropper if it isn't good enough for the test ? The only way to meet this requirement to the fullest is to use a calibrated semiautomatic pipette.
  8. Eek ! I hope they don't need transfusion.
  9. Oops. Perhaps "Mia" is not as obsolete as I believed. Great article/reference.
  10. Yes. In the examples I've seen, the usual the culprit is a gene re-arrangement that results in expression of the Dantu antigen. If I remember correctly, the P3BER clone does not react with Dantu+ cells. If it isn't mentioned in the Directions for Use, you could check with the technical people at Millipore/Bioscot. The presence of "Mia" (an obsolete umbrella term that can apply several "Miltenberger" antigens), already indicates that some MNS gene shuffling has occurred.
  11. Do you mean used to MAKE the eluate or it being added to the test system ?
  12. This scenario doesn't explain why the donor red cells react with the serum from most patients. For this to be a "low incidence antigen" issue, ALL of the patients would have to have an antibody to (probably) the same low incidence antigen. That is very unlikely. As Malcolm suggests, this sounds like an abnormality of the donor's red cells. I believe Hemo bioscience have a lectin kit, but it may only be available in the USA.
  13. NicolePCanada - I agree with both Ward_X and Malcolm's comments. There are definitely situations (patient groups, diagnoses) where a less sensitive methodology like LISS-IAT can be useful to work around "junk" that may be detected in Gel, Solid Phase or PEG test systems. But...they should be employed only by operators who understand the consequences of such actions, AND have the support of their medical staff.
  14. The "Swiss Army Knife" approach to serological problem solving used to be fun. Having the ability to tinker with a variety of test methods and come up with your own conclusions was one of the addictive parts of immunohematology. Alas, that is no longer viable in today's era of validate everything and demonstrate competency several times a year. I used a lot of words to say: "If you don't use it, get rid of it".
  15. I like your "neo-science" quote ! As the actual science has progressed, and the sensitivity of assays has increased, workers have encountered "-only" antibodies: albumin-only, enzyme-only, LISS-only, PEG-only, solid-phase-only, Gel-only. As you point out, if the older assays were that bad, we'd have patients dropping all over the place due to the presence of "missed" antibodies and false-negative crossmatches. My point about the "stickiness" is that the gel system is notoriously unforgiving with anything but completely normal, healthy, well-washed cells, preferably in the manufacturer's diluent. Throw anything at it that's little different and you risk incomplete or unsatisfactory centrifugation of red cells. I don't know if that specifically happens with Jk(a-b-) cells, but I have seen frozen/thawed cells behave badly. After reviewing the posts here , I think it's perhaps a little more worrying that jojo808's group may consider transfusion of "least-incompatible". I understand that needs must, but that's a dangerous proposition if one doesn't know the specificity of the antibody(ies) causing the incompatibility.
  16. This may be a little heretical, but I think I would avoid the gel test in this case. Perhaps do the cross-matching in a test system that's not as sensitive ? Local policy permitting, of course. A plain old tube test would probably result in compatible crossmatches. The gel test system has probably not seen many cells with the Jk(a-b-) phenotype, and I also suspect that they're probably "sticky", especially if the cells have be frozen/deglycerolized.
  17. Reactivity with two of three cells effectively rules out the "antibody to a low incidence antigen" argument. Is the supplier/manufacturer of the Screening Cells the same as the supplier/manufacturer of the panel ? If not, then I suspect formulation differences of the two products may be the answer, specifically pH of testing environment.
  18. It's tough to see on the scanned panel sheets, but the D- group O panel cells are w+ reactive, equivalent reactivity to the crossmatched group A cells.
  19. Agree with previous - looks like a warm autoantibody and it's important to see what, if anything is underneath. Adsorptions will be necessary. Interestingly, if I can read the results correctly, the antibody is showing a marked preference for D+ cells. It may have LW specificity, although 4+ is unusually strong for anti-LW. I'm curious as to why there is "w+ incompatibility with all A pos units". I would have expected those to be 4+ reactive, also. There may be several issues going on here.
  20. Exactly. And very likely to cause in vitro hemolysis in appropriate test systems (not to mention in vivo hemolyis). I remember doing many 2-stage EDTA tests, using fresh complement and poly AHG. Good times. I think I may have met Dr. Cedergren when I was working at the BGRL in Oxford during the late 1980's.
  21. I can't really explain your serological findings, but I agree with Malcolm's sentiment: "That stuff'll kill ya!" Anti-Vel is notoriously slippery and infamously dangerous. Without a more detailed look at your results, I see a few remote possibilities: 1. The anti-Vel may have an IgM component that doesn't like the Gel, but does like the PEG test 2. There's possibly something underlying the anti-Vel, hence the "extra" reactivity 3. The unit you crossmatched is not actually Vel-, but another member of the Vel variant club
  22. While the use of EDTA plasma basically eliminates the chance of detecting hemolytic antibodies (as Malcolm says above), some laboratories still use serum. It's possible some hemolysis might been seen in visual check before taking the serum-RBC-PEG reactants to IAT. One may also recognize loss of RBC volume after the washing process, if some of the cells were destroyed during the incubation phase.
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