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Clarest last won the day on July 9 2017

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About Clarest

  • Birthday 10/21/1971

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  1. Thank you Ensis01 for your response. We do not do weak D testing if the patient has a positive DAT. We only do weak D testing on the cord blood samples when possible. However, I would like to know how you would interpret the weak D testing when the patient has a positive DAT. Based on the inserts of the RhD typing reagents we used, there are the following statements. "An Indirect Antiglobulin Test result with cells that demonstrate a positive Direct Antiglobulin Test cannot be reliably interpreted with respect to weak D." "A positive Indirect Antiglobulin Test for weak D must be validated by a macroscopically negative direct antiglobulin test or a negative indirect antiglobulin test using an appropriate control." Red blood cells coated with alloantibodies or autoantibodies of the same or similar specificity as the reagent (i.e., cells that are DAT positive) may give weak reactions. This is due to decreased availability of antigen sites because of antigen blocking or steric hindrance. In extreme cases, false-negative results may occur.
  2. I have more questions on this topic. 1). Is the monoclonal control only required for AB pos cord but not for full blood grouping test (including forward and reverse grouping)? 2). Is the monoclonal control required for weak D test? For what I understand, the monoclonal control is mainly used to detect spontaneous agglutination that could cause mistyping. If your RhD typing at immediate-spin is negative (or even there is negative reaction with ant-A and/or anti-B reagent), does that prove there is no spontaneous agglutination? If yes, what's the purpose of using monoclonal control in the weak D test?
  3. Even with a AB+, if the forward matches to the reverse grouping, I am wondering if the control is still needed.
  4. Thank you Malcolm and David for sharing your experience with me.
  5. I totally agree with exlimey for keeping LISS-IAT as a backup and less sensitive method to the more sensitive ones like solid phase and others. Since the LISS-IAT is our backup method, we usually use it after the first solid phase panel combined with a tube DAT as no autocontrol is set up with the solid phase panel. Now, we are having a debate on whether we need to follow the statement on the Gamma N-HANCE package insert "An autologous control ... is recommended for compatibility and antibody identification tests." I was thinking that if the DAT has already been done on the same specimen, we do not need to set up an autocontrol when using the LISS IAT. As a common Blood Bank practice, when an autocontrol is positive, a DAT is the next step to differentiate if the positivity is an in vitro or in vivo phenomenon. However, there could be a scenario that the specimen has a positive autocontrol but negative DAT (DAT-negative AIHA?). If as what I thought in above, that means we might miss this type AIHA. In fact, our current practice (no autocontrol set at all) before switching to Gamma N-HANCE from ImmuAdd, we have missed this Any input on this debate will be much appreciated!
  6. Hi Malcolm Needs, I would like to see an explanation for “why” on the package insert. Unfortunately, no! It only mentions an optical aid may be used. I am afraid of over reading by the staff. Particularly, we are planning to use this enhancement medium in our IAT corssmatch. Currently, we use saline IAT crossamtch. By the way, how would you define a microscopically positive reaction. How many cells clumping together would be a positivity. I find some staff even call occasionally seen “kissing cells” a positive reaction.
  7. Hi Kathyang, When you use either ImmuAdd or Gamma N-Hance, do you do the microscopic check for the negative reaction at AHG phase?
  8. Hi, our lab has the same situation as yours. I am wondering if you do the microscopic check for the negative reaction at AHG phase when using LISS enhancement. On the ImmAdd package insert, it doesn't mention the use of an optical aid, but the N-HANCE one does. Thank you in advance for your response.
  9. Our PreAdmit patient samples are valid for 30 days after collection if patients have not been pregnant or transfused in the last 3 months. We usually perform the group and screen test on the day of collection and if applicable, antibody workup ASAP. If required, we usually do the crossmatch one the day before the scheduled surgery date. Previously, we had separated plasma from cells for all samples. After we did validation to show that the reactions strength of ABO antibodies in the unseparated samples on their 30th days is comparable to that in the separated plasma, we stopped separating plasma if the antibody screen is negative and only immediate-spin crossmatch is required.
  10. Below is the source of my 1st question. " If the patient has been transfused within the past three months, but not within the last three weeks, an elution may be omitted if all of the following apply: a). The DAT was positive on the last specimen tested (i.e. collected more than three weeks ago) and was investigated, and b). The positive DAT (i.e. strength of the reaction) on the current specimen is not stronger than the DAT performed on the last specimen, and c). The antibody screen (i.e. strength of the reaction) on the current specimen is the same as on the last specimen. Note: Clinical circumstances, evaluation of transfusion, test result history and/or specimen history may override the above criteria and elution may be desirable for selected patients." Could any one explain why "three weeks" is specified here but a longer or shorter duration? Thank you.
  11. Hi Malcolm, Look at what I found in the link below http://www.transfusion.ca/Resources/CSTM-Blog/January-2017/I-will-remember-you-Malcolm-Needs Clarest
  12. Hi Malcolm, 1. I agree with you if we suspect there is a transfusion reaction which causes the positive DAT with IgG, it makes sense to do an elution on the new sample in case some other antibody(ies) are being detected this time but not from the previous sample. 2. Even we test an eluate once every month for the patient with an autoantibody, it is exactly as what you said the eluate shows pan- agglutination. Unfortunately, we do not perform alloadsorption on site. So, the eluate really does not mean that much for detecting underlying alloantibody(ies) developed due to transfusion reaction, especially when the auto is strong and the eluate always shows 3 to 4+ reaction strengths. Do you think it's necessary to send to our Reference Laboratory once every month for an alloadsorption or just send out when there is a sign of hemolysis process going on? Clarest
  13. We do exactly the same as Laurie said. I would like to take this opportunity to do another survey related to elution studies. 1. After a patient was transfused a couple of days or a week ago, we received a sample and did elution on it due to positive DAT with IgG. Then, several days later (no transfusion after the last elution) , another sample was received and the DAT was still positive with IgG. Do you do another elution as the patient has been transfused in the last 3 months? 2. If a patient has an autoantibody ( DAT is always positive with IgG) and has been frequently transfused (please do not ask me why?), do you do the elution on every post-transfusion sample received (e.g., every 96 hours or weekly) before crossmatching for the next transfusion? If not, how often do you perform the elution if the positive DAT (i.e. strength of the reaction) on the current specimen is not stronger than the DAT performed on the last specimen, and the antibody screen/panel (i.e. strength of the reaction) on the current specimen is the same as on the last specimen? Thank you.
  14. As Malcolm mentioned " as the anti-B in those units tend to be of lower titre and avidity than does the anti-A in either group B or O units". The patient is group AB and the red blood cells have A and B antigens.
  15. Hi Mabel, We use the tube saline IAT method for crossmatch and it is allowed to skip the immediate-spin phase. So, as long as the anti-A1 does not react at 37C, we have no problem to result the compatibility of the crossmatch. Routinely, it is okay for us to give group O or B blood for patient's with anti-A1 and that's what technologists prefer to do as it only requires immediate spin. However, for this particular patient, we just wanted to be more careful. Clarest
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