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exlimey

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Everything posted by exlimey

  1. I agree, Brenda. Immucor does a relatively good job of indicating changes. It can get a little ugly when the same "new" insert (with highlighted changes) is still being issued many years after the change. Perhaps Immucor buys a minimum number of inserts with highlighted changes and at some point transitions to the "clean" version ? In the recent years, in the wake of mergers and consolidations, I've noted that the changes are often just name, logo, address or telephone numbers - of no real impact to the average user (unless you need to call Customer Service, of course).
  2. The short answer: Money - throwing stuff out is expensive. The long answer: To get a good price for printed materials (package inserts, labels, etc.), one must purchase tens of thousands of copies. If changes are required, but not especially critical, the regulating bodies (FDA) will allow manufacturers a fair amount of leeway to use up current stock. Throwing out anything has an associated cost and since the commercial manufacturers are in the for-profit arena, they will tend to shy away from such actions. I'm sure this contributed to Immucor's tardiness. Another contributor to slow moving changes: In the US, any changes to a package insert (or label) must be approved by the FDA before that new document is distributed. This process can take 6 - 12 months depending upon the complexity of the changes and the number of times the document goes backwards and forwards between the two parties.
  3. Reagent red cells certainly do not "express antigens weakly". There is no way a commercial entity would risk distributing a product that might give rise to customer complaints - the regulating bodies (the FDA in the USA) would be all over those issues. There may be some weakening of antigen strength over the life of commercial red cell products, but this weakening would probably only be noticed with a borderline, wishy-washy antibody - perhaps you have stumbled upon such a beast. Commercial reverse cells (A1, A2, B, O) are washed extensively before preparation of the products. Additional washing will not "uncover more antigen sites". At most, washing (with saline) will remove the commercial red cell diluent/preservative and change the chemical environment of the test system. This change may indirectly enhance or suppress reactivity of some antibodies. If you are using unwashed cells in ABO tests, remember that ABO substance will also be in the plasma/serum and may neutralize an antibody before it has a chance to bind to the red cells. In such a case, washing will definitely enhance reactivity.
  4. Red cells that contain HbSS (or HbSC) are more resistant to hemolysis in hypotonic environments than cells carrying "normal" hemglobin. This makes it a useful technique to recover autologous cells from transfused sickle cell patients (providing the patients have some level of native RBC production). It is not useful for harvesting autologous cells from transfused patients who do not have HbSS. A reference: A Rapid Method for Harvesting Autologous RBCs from Patients with Hemoglobin S Diesease. Brown D., Transfusion 1988; 28:21-3
  5. Sandy, How do you deal with discordant results? There's a great difference in sensitivity of the assays you mentioned. Or do you bias the results beforehand by making sure your test samples perform in each system? Not a criticism, just wondering.
  6. Perception is important, but education can help smooth over the concerns. I think it's important to remember that the outside of the bag "lost it's shine" as soon as it left the shipping box and was used to collect blood. There is nothing sterile about a church hall, a high school gymnasium or any other of the myriad of places blood is collected. I wonder how hospitals reconcile the fact that "dirty" blood bags are transported into and used in their super-clean surgical suites ?
  7. A valid point. It is not uncommon to find a spurious positive DAT in a sample collected in EDTA tube, especially in "older" tubes. My point is that crossmatches use segments (pigtails) and the presence of the sugary-goodness in the collection systems can also cause positive DATs.
  8. I agree with Malcolm's comments and would add that I suspect that many positive DATs in donors occur after collection of the blood, i.e., the donor is not actually DAT+ in vivo, but somehow the red cells pick up globulins during exposure to the chemicals and environment of the collection system.
  9. sbazel - bad idea to use the earliest expiration date of the components of your cocktail. Neither apply to your working reagent. Certainly the anti-D has been grossly modified from its original. To assign a genuine expiration date to your cocktail, you would be obliged to perform a formal stability protocol.
  10. If you are using a commercial anti-D reagent as your starting material, you might be creating your own problems. Most reagents are now monoclonal and as such they often have very peculiar formulations (additives, diluents, etc.) that ensure their stability. When end users dilute or otherwise modify the reagents, they may lose the key element required for reactivity and/or stability (even when frozen). I suggest you try a polyclonal (human) source (which is probably what Malcolm's group is using). If you need to dilute it to get to the desired reactivity, I recommend using either inert normal human serum or 6% BSA. Both diluents should maximize your chances of stability, either in the liquid state or frozen.
  11. Winter - in the case of DARA patients, the DTT is use to treat (panel or screening) cells rather than the serum. SMILLER - do you enzyme-treat your own cells ? If so, have you determined their stability ?
  12. You will probably need to "qualify" the vendor is some fashion, but I don't believe you have to do any serological comparisons providing you are going to use the material according to the manufacturer's directions.
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