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New Lot Immucor FMH Rapid Screen


David Saikin

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Anyone finding that the positive control for this assay has significantly smaller rosettes than previously encountered? 

 

I am.  Tested with the old lot anti-D and the new Pos Ct - very weak.  Tested with the new lot anti-D and the old Pos Ct - usual strength.  Tested new lot anti-D and new lot Pos Ct - very weak.  It's got to be the new lot Pos Ct.  Used the new lot Indicator Cells for all testing.

 

My initial reaction to this assay was that the pos ct was NOT positive.  I finally could make out rosettes of about 5-6 cells - very difficult to see.  Immucor had no resolution and only one other comment on file that the rosettes were a lot smaller than usual.

 

This is hard on a staff of all generalists.

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David

We have had poor reactions with the current lot of Immucor FMH Rapid Screen. I ordered a new kit from Immucor, thinking something happened during shipment and the new kit (same lot) is equally as bad. We have moved all testing to K/B until a new lot comes out.

We have made multiple complaints to Immucor throughout this week.

Alana

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I had to repeat a patient x3 yesterday to get the positive control to work. Don't know why as I did the same thing each time. I did look closely for smaller rosettes in the failures (hoping they were really positive after all) and didn't see any. Once it worked I got the same number that I expect to see in a positive control. They might have been a bit smaller, but they were still highly visible.

 

I have noticed that the rosettes are more fragile than the old Immucor fetalscreen test - I tell my techs to shake out the tubes very gently and to spread their test drop on the slide only by tilting. I've also heard a small amount of grumbling from a couple of techs who do many of the fetalscreens here about having to repeat tests due to failure of the positive control. I've observed them and their technique looks good - no obvious reason for problems. I've got an evening tech who always reports out twice as many rosettes for her positive control as anyone else. I've looked at her controls - her positives are really positive, same size rosettes as I get. Her negative controls are always good and she doesn't report out 'false' positive patients. Her technique is very delicate, so that may be the key.

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David

We have had poor reactions with the current lot of Immucor FMH Rapid Screen. I ordered a new kit from Immucor, thinking something happened during shipment and the new kit (same lot) is equally as bad. We have moved all testing to K/B until a new lot comes out.

We have made multiple complaints to Immucor throughout this week.

Alana

Yes - I rec'd a new kit also; with the same results

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I have also noticed that the positive control is a lot weaker than the last lot. 

 

"Did anyone have the opposite from within the last few months? Where fetal screens came up positive but the KB was negative?"

 

Goodchild, do you check mothers for Du when you have a positive FMH before sending it out?  That happened to us a couple of times before we implemented testing for weak D into the procedure if the result is positive.  If the Du is positive, we report the test is invalid and send it out for Fetal Hgb F.

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we had same problem once before and we prepared positive control in house once a week. We ran in house control against old lot and then used in house prepared positive control.

 

There is a thred on this forum with formula on how to prepare the positive control. May be David posted it!

 

We prepared it once a week and we only run control if we have a patient and we get one patient a week and we do not have 24/7 staff to run KLB so we had to find a way to do fetal screen...

Edited by Eagle Eye
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I found the formula in the technical manual:  1 drop of 2-5% Rh positive control cells and 15 drops of 2-5% washed Rh negative control cells. Add 1 drop of this suspension to 9 drops of 2-5% washed Rh negative control cells.  I'm going to mark it in case I ever need it.

Edited by mollyredone
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I don't see how you can make your own control for this kit and be in compliance with CAP Standards - mixing reagents from different lots is verboten - making your own reagent seems, to me, to be even more of a regulatory compliance issue . . . esp if you mention it to the FDA.  If I inspected you I would cite this practice

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I don't see how you can make your own control for this kit and be in compliance with CAP Standards - mixing reagents from different lots is verboten - making your own reagent seems, to me, to be even more of a regulatory compliance issue . . . esp if you mention it to the FDA.  If I inspected you I would cite this practice

 

We make our own positive controls too for KB slides. We use 1:10 dilution of cord cells with an adult male, then a 1:10 dilution of this mixture with further adult male cells. We then use this mix and the adult male in a 1:2 dilution with saline.

 

As far as I am aware there isn't a commercially available control in the UK.

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We also make our own positive and negative controls for KB staining, but this follows the manufacturer's recommendation.  Since the instructions for use of the Fetal Screen kit are to use the controls cells provided in the kit, to do otherwise would be a deviation from the instructions.  You would need to perform a validation in order to deviate from manufacturer's instructions and have it approved by your medical director.

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We make are own pos ctrl for KB slides too - it is part of the manufacturer's directions.  However, above you are talking about an integral part of a kit . . . I think that even if Immucor gave you the formula for making it AND their diluent AND any other pretreatment they utilize you still would be in violation of the CAP standards for kit tampering. 

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Did anyone have the opposite from within the last few months? Where fetal screens came up positive but the KB was negative?

 This is not an uncommon situation. For quite a few years, I was in charge of a prenatal testing lab at Memorial Blood Centers. One of the services we provided was Kleihauer-Betke testing. For quite a few years we repeated FMH screens on samples submitted for Kleihauer-Betke testing due to pos FMH screens when the Kleihauer-Betke test was negative. We followed the FMH screen procedure published by Betty Sebring, who, also, worked at Memorial. In all cases, the FMH screen test in our hands was negative.
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