Use of negative (diluent) control in blood grouping

[k1065 13]

I wanted to get some other opinions on this subject -

Guidelines say that a diluent control should be used if the antisera used in the grouping contain potentiators, if a cold auto-antibody is present or where it is recommended by the manufacturer of the reagent. Please correct me if I am wrong here.

Most (if not all technologies) incorporate a negative control directly as part of the test. So, assuming the test is automated, without the option to add a control to each test, how would people feel about the removal of this control?

Thanks

[Malcolm Needs ★ 4,910]

Very, very worried.

[k1065 13]

Hi Malcolm,

Totally agree! Hence the worried face at the end of the original post.

Edited February 24 by k1065
Ammended comment

[jayinsat 163]

I don't follow. Like you said, all the available automated platforms incorporate a monoclonal control in blood typing. Are you suggesting removing the monoclonal control from the blood grouping test on automated platforms?

[galvania 804]

well yes and no.  It would depend what the test was.  The typical test not offering controls would be an antibody screen.  As most of these are negative or positive with only some of the cells, this acts as its own control.  Where you would need to perform a 'negative' control is if all screening cells are positive.  This would be done by carrying out an auto-control with the panel.  If that is positive too, however, you still won't know, in the absence of any other information, whether the patient has a true auto-antibody or whether the patient is reacting because of the potentiator in the AHG / diluent.

For antigen testing, a must however, especially if tested in an IAT or with enzymes

[jayinsat 163]

2 minutes ago, galvania said:

well yes and no.  It would depend what the test was.  The typical test not offering controls would be an antibody screen.  As most of these are negative or positive with only some of the cells, this acts as its own control.  Where you would need to perform a 'negative' control is if all screening cells are positive.  This would be done by carrying out an auto-control with the panel.  If that is positive too, however, you still won't know, in the absence of any other information, whether the patient has a true auto-antibody or whether the patient is reacting because of the potentiator in the AHG / diluent.

For antigen testing, a must however, especially if tested in an IAT or with enzymes

I believe he is asking about blood grouping. That is what the title of the message suggest, "Use of Negative Control in Blood Grouping." 

I'm so confused.

[galvania 804]

true.  Should have read that more carefully.

Well the answer is still - yes and no.  If you are using monoclonal reagents, and assuming the anti-D has the same formula as the other reagents (barring the actual antibody obviously) then most results will have at least one negative well that can serve as a control in any case.  You could just then put up a neg control on the AB+ results.  But the majority of cards/cassettes do have a control on them anyway.  If there's only anti-A-B-D, that's only supposed to check a group that is known i.e. has already had at least one full group with a control.  But there too - only a problem if AB+.  And if you are using an Rh pheno card, the control well on the grouping card is valid provided that the formula for all reagents is the same

[k1065 13]

Thank you all for your comments.

To be clear, I do not advocate the removal of the control from the blood grouping test; automated or manual.

My interest was sparked following a group conversation on this topic where I was surpried to find that some folk would be comfortable to omit the control, and rely solely on forward vs reverse typing as a check. They were less certain when I challenged them with the scenario of a discrepant blood group!