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dwalters

Gel card with 1+ reactions showing negative after spinning a second time

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All 3% cells, regardless of the manufacturer must be diluted with MTS diluent 2 when used for Gel antibody detection or identification.

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All 3% cells, regardless of the manufacturer must be diluted with MTS diluent 2 when used for Gel antibody detection or identification.

Yes, I know that. Not sure who/what this response was meant for....

For my part, I only said Immucor because they are the other primary Manufacturer for Blood Bank Reagents, and we do get their 3% Screening Cells and 16 Cell Panel.

Brenda Hutson, CLS(ASCP)SBB

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Well, I really don't think that Ortho is going to share their proprietary recipe for MTS Diluent 2 with their chief (or any other) competition. Yes, it's a pain to have to dilute up cells to use with gel, but we do it, too. We like the results better that way.

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Well, I really don't think that Ortho is going to share their proprietary recipe for MTS Diluent 2 with their chief (or any other) competition. Yes, it's a pain to have to dilute up cells to use with gel, but we do it, too. We like the results better that way.

Well, if we can successfully dilute the 3% cells to 0.8%, why wouldn't Immucor be able to do that? I don't think it is the technology. The Immucor Rep. said it just looks like a conflict of interest for them to make cells that support Ortho's product.

Brenda

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We have had this problem too- we know that they are almost always really negative because we are still in our test phase of doing antibody ID's in house and must send all positives to another lab. We send our results but they seem to always re-dun the screen and over 90% were negative to begin with, causing us much more work. Also noticed that one month was worse than another- different screen cells. We only have 1 tech to run so adding 20 ID's a night is significant for us. Does spinning the cards upon receipt really help??

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Dear bbnewbie

If 90% of your positives are really and truly negative then you have a problem somewhere along the line that needs to be sortedout. It migt well be that the lab you are sending the results to are using aless sensitive technique but it might also be a number of other things - for example, that your centrifuge is incorrectly calibrated, that your gel cards have dried out (thereby concentrating the Coombs), that you are pipetting too many cells (either too much volume or an incorrect cell suspension), or there is something wrong with the diluent you are using.....I'm sure there are other possibilities but I haven't had my second cup of coffee yet this morning - brain's not yet fully in gear

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The fact that a second spinning of a gel card can create a negative impression in a gel column of a weak reaction should not suprise any experienced immuno hematologist. The practice of placing any credibility in a result after a second spin seems reminiscent of technologists who using tube testing would shake a weak reaction away. I whole heartedly agree with those who are advising to follow the manufacturers guidelines and interpret reactivity after a SINGLE spin only.

Weak reactivity of an antibody with low avidity can easily be dispersed. I would guess this is what is occurring after a second spin. Weak reactivity and low avidity do not always translate to clinically insignificant.

Having observed the phenomenon described (i. e. weak reactivity becoming negative) many times when using a gel card on subsequent patients would lead me to believe this can occur easily. Furthermore, it should not be interpretted as a negative result nor should not be considered clinically insignificant until an appropriate workup is performed.

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When we get questionable results, we respin the sample and incubate the screen for 30 minutes (max is fourty). Most of the time this clears up the situation. I feel that rouleaux is hard to read in the gel cards and we do spend too much time chasing the ghosts of reations that are non-specific.

:confuse:

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The fact that a second spinning of a gel card can create a negative impression in a gel column of a weak reaction should not suprise any experienced immuno hematologist. The practice of placing any credibility in a result after a second spin seems reminiscent of technologists who using tube testing would shake a weak reaction away. I whole heartedly agree with those who are advising to follow the manufacturers guidelines and interpret reactivity after a SINGLE spin only.

Weak reactivity of an antibody with low avidity can easily be dispersed. I would guess this is what is occurring after a second spin. Weak reactivity and low avidity do not always translate to clinically insignificant.

Having observed the phenomenon described (i. e. weak reactivity becoming negative) many times when using a gel card on subsequent patients would lead me to believe this can occur easily. Furthermore, it should not be interpretted as a negative result nor should not be considered clinically insignificant until an appropriate workup is performed.

Yes, pre-spin before testing and post- spin after the test has been performed should be clearly differentiated. One must never post-spin.

Liz

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I've heard that at some facilities, a negative second spin is thought to be an indicator for cold antibodies. I'm guessing the same might be true for weak rouleaux. Personally, I wouldn't take much credence in a second spin. If you think about the nature of the gel beads in this method, it makes sense that a second spin of an already weak reaction, might just compact things enough to be negative.

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Goodness gracious (or something like that) - I ask the second spinners - show me the reference! That is what regulatory authorities will ask! Let's put this thread to bed. If you have a reaction you must do something about it!

Eoin

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Goodness gracious (or something like that) - I ask the second spinners - show me the reference! That is what regulatory authorities will ask! Let's put this thread to bed. If you have a reaction you must do something about it!

Eoin

I thoroughly agree - and spinning the card a second time is NOT doing something about it!

:eek::eek::eek:

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I contact with ortho about this and they reply :

"

I assume you are doing your crossmatch in gel.  If you see any agglutination above the negative red cell button the result is positive.  And NO – you cannot respin the card and re-read it.  Additional spin time can make a true positive become negative.  Hope this helps.

Regards,

 

Dee Landers

Technical Specialist III

Ortho Care Technical Solutions Center

  "

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We don't re-spin the card , we re-spin the sample.  If this doesn't work here is our process

>Perform a full gel panel with auto control

>If not pattern, no antibody identified(some cells pos/some negative)

   >not all clinically significant antibodies r/o consult tech specialist or technical lead
   >all csa ruled out report as an "no significant antibody" and use gel xm

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On ‎4‎/‎1‎/‎2006 at 12:43 PM, dwalters said:

An ER trauma patient's plasma showed 1+ reactivity in Gel with Screening cell 1 of Immucor's Trio screen. The other two cells were negative. (We buy 3% Immucor screening cells, then dilute them to 0.8% for gel testing.) Using an Ortho 0.8% panel for antibody identification, we found 7 of the 11 cells reacting 1+ with a negative auto control. The reactions did not fit any pattern what-so-ever. Our workup was stopped at that point because the patient was transferred to a larger facility. On follow-up the next day, we found that the other facility had gotten a negative antibody screen, also using Gel cards. Within three hours of performing the antibody screen on the ER trauma patient, the remaining three wells of the gel card were used to perform an antibody screen on another patient. So, the card with the positive Screening cell 1 was spun for another 10 minutes. After the 2nd spin, the reaction had changed to negative. Later, we spun the two cards containing the antibody id with the seven 1+ positive reactions. After the 2nd spin (for a total of 20 minutes) most of the reactions were now negative with the others only questionable, definately not 1+ as after the orginal spin.

I've checked the rpms and timer on the centrifuge, and they are okay. Has anyone else seen positive reactions change to negative after spinning a second time?

No, because, unlike tube testing, you cannot spin a gel test twice.  Part of the calibration of the gel test, aside from the pipetting 'exact' amounts, is 'this is how far the cells migrate through the gel beads at this speed for this period of time', i.e. second spins cannot 'count' because to do so, you have violated the requirements of the test.

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I have noticed that if my gel reactions start to look hazy after centrifugation that the card I keep as a balance card may be getting extremely dried out.  After I replace it with a new card my reactions are clearly negative.  Could it be a problem with the balance of your centrifuge or it may not be level?   

We sometimes get the weak reactions that are absent after a second spin but they are mostly from OB patient's post midterm RHIG.  We do not use a readings after a second spin.

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2 hours ago, Patty said:

I have noticed that if my gel reactions start to look hazy after centrifugation that the card I keep as a balance card may be getting extremely dried out.  After I replace it with a new card my reactions are clearly negative.  Could it be a problem with the balance of your centrifuge or it may not be level?   

We sometimes get the weak reactions that are absent after a second spin but they are mostly from OB patient's post midterm RHIG.  We do not use a readings after a second spin.

Thanks for the tip!  We have not had any particular problems but we will refresh the balance card!

Scott

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