Weak Rh Positive and DCT or control positive

[khalidm3]

Some times we have a blood donor whose Direct Rh test is Negative but his weak Rh test (Du) positive while DCT/Rh Control also positive.

We try gentle heat elution but usually it is of no benefit.

What is the best technique to determine his Rh.

Do u face this problem?

Thanks

[David Saikin]

Sounds like your donor has a positive Direct Antiglobulin test (direct Coombs'). The unit should not be released to a transfusion service. If you really want to know you can try to absorb and elute anti-D from the red cells.

[khalidm3]

sure we discard the unit, but what result for Rh for the Donors. Please refer me to the procedure for Absorption and elution for anti D. I try gentle heat elution and rarely I get DCT positive and the problem is solved but it is not always successful.

[JOANBALONE]

Hi khalidm3,

Do you have access to chloroquine diphosphate? If you do there is a procedure in AABB Technical Manual for Dissociation of IgG by Chloroquine for Red Cell Antigen Testing of Red Cells with a Positive DAT.

[khalidm3]

Sorry we do not have chloroquine. I will check it also

Thanks

[David Saikin]

Just generically - rx equal volumes of your donor red cells and anti-D; also run using Rh+ and Rh= cells as controls. (1 mL should suffice). I'd incubate at 37C for 15 minutes, but that is up to you. Wash the cells 6x. Perform standard elution on all and test eluate for anti-D reactivity (also test the eluate from Rh+ and Rh= cells: the Rh+ should show anti-D, the Rh= should show no D reactivity). Also remember to test each last wash as a control for your elution. I cannot point you to a formal procedure for this.

Anybody else?

sure we discard the unit, but what result for Rh for the Donors. Please refer me to the procedure for Absorption and elution for anti D. I try gentle heat elution and rarely I get DCT positive and the problem is solved but it is not always successful.

[khalidm3]

Thanks David, I am used to do adsorption-elution for week A or B, but this the excellent thought from you.

[Maximiliano]

Have you consider a molecular test for identifying/confirming RhD status?

[Malcolm Needs ☆]

Have you consider a molecular test for identifying/confirming RhD status?

I thought that, but not everyone can get access to this technology.

[Maximiliano]

Thanks Malcolm.

That is true and I thought of it right after sending my message. However, there are a lot of labs around the world that could provide that service. The closest to Riyadh, where I believe khalidm3 is based, that I know is in Kuwait.

[Malcolm Needs ☆]

Thanks Malcolm.

That is true and I thought of it right after sending my message. However, there are a lot of labs around the world that could provide that service. The closest to Riyadh, where I believe khalidm3 is based, that I know is in Kuwait.

True.

[khalidm3]

I thought that, but not everyone can get access to this technology.

Same here, it is just in our thoughts.

[Eagle Eye]

do you have immucor supplier in your area? They have chloroquin...

[khalidm3]

do you have immucor supplier in your area? They have chloroquin...

Yes, but I am working in a governmental hospital, purchase is not so easy. I will try David procedure, more appealing to me.

[David Saikin]

You know, everyone is so hot for molecular testing . . . it sounds really neat BUT everytime I investigate it the cost is prohibitive . . . esp for determining the Rh of a donor - seems exhorbitant.

[Marilyn Plett]

Before I retired, my blood center was charging around $650 which was the amount that hospitals could recoup from insurance payments. If you're talking about investigating patients with warm autoantibodies, the cost of multiple absorptions and cell treatments to remove IgG vs molecular testing could work out about the same.

[Maximiliano]

You know, everyone is so hot for molecular testing . . . it sounds really neat BUT everytime I investigate it the cost is prohibitive . . . esp for determining the Rh of a donor - seems exhorbitant.

Molecular testing can be costly, true, but what is the cost of reliable identifying Rh on a donor such as the one of this case?

[David Saikin]

I am not going to use the donor so I don't really care what the Rh type is . . . if the DAT is negative next visit, the Rh will be uncomplicated; if the Rh is still problematic next visit, I'm still not going to use the donor . . . kind of pragmatic but I wouldn't bother in this instance.

Molecular testing can be costly, true, but what is the cost of reliable identifying Rh on a donor such as the one of this case?

[Maximiliano]

I am not going to use the donor so I don't really care what the Rh type is . . . if the DAT is negative next visit, the Rh will be uncomplicated; if the Rh is still problematic next visit, I'm still not going to use the donor . . . kind of pragmatic but I wouldn't bother in this instance.

Hi David,

Thanks for your message.

That's a good way of looking at the issue. Certainly, very pragmatic and what most blood banks do.

However, what's the cost of that blood unit you're disposing? And what's the cost of the 2 blood units you'd be disposing if the donor returns? Wouldn't just that justify the investment in a molecular test?

Sorry I'm playing the devil's advocate here, but I'm enjoying the discussion. Again thanks for your views.

Regards

[Malcolm Needs ☆]

Just to be another devil, what would be the cost if the donor turned out to be D positive, but the unit was transfused into a D negative female of child-bearing potential, she made an anti-D, lost the baby and then sued????????

I am very much in agreement with David on this one.

Take NO chances.

[Dr. Pepper]

Just generically - rx equal volumes of your donor red cells and anti-D; also run using Rh+ and Rh= cells as controls. (1 mL should suffice). I'd incubate at 37C for 15 minutes, but that is up to you. Wash the cells 6x. Perform standard elution on all and test eluate for anti-D reactivity (also test the eluate from Rh+ and Rh= cells: the Rh+ should show anti-D, the Rh= should show no D reactivity). Also remember to test each last wash as a control for your elution. I cannot point you to a formal procedure for this.

Anybody else?

Assuming the initial problem was a positive direct antiglobulin test due to an autoantibody, most likely a panagglutinin, isn't there a good chance that the eluate will react with all panel cells due to the autoantibody, making it difficult to see the anti-D in there? If there isn't a clearcut specificity for anti-D, one might want to titer the eluate against a Rh+ cell and a Rh- cell in hopes of finding better a higher titer (or not) against the Rh+ cell.

This is, of course, to try to satisfy the insatiable blood banker's curiosity that we all possess. We want to know the answer to the problem! As was stated, you're not going to use the unit. (And I must admit that we do have a computer entry choice for blood type results, used with extreme rarity, reluctance and sadness, "Unable to determine".)

[Malcolm Needs ☆]

If there isn't a clearcut specificity for anti-D, one might want to titer the eluate against a Rh+ cell and a Rh- cell in hopes of finding better a higher titer (or not) against the Rh+ cell.

The trouble is, an auto-anti-LW, more common than most people think, will give very similar results, and you still will not know if the red cells are D+ or D-.

Sorry to muddy the waters.

[Dr. Pepper]

Good point, Malcolm. You once called anti-P1 the forgotten antibody, I think anti-LW might qualify as well.

[David Saikin]

I actually sent Khalid a private message to this effect. It might be medication induced, in which case there is a reasonable chance that it may not be a "pan". But I did warn him anyway . . . JIC.

Assuming the initial problem was a positive direct antiglobulin test due to an autoantibody, most likely a panagglutinin, isn't there a good chance that the eluate will react with all panel cells due to the autoantibody, making it difficult to see the anti-D in there? If there isn't a clearcut specificity for anti-D, one might want to titer the eluate against a Rh+ cell and a Rh- cell in hopes of finding better a higher titer (or not) against the Rh+ cell.

This is, of course, to try to satisfy the insatiable blood banker's curiosity that we all possess. We want to know the answer to the problem! As was stated, you're not going to use the unit. (And I must admit that we do have a computer entry choice for blood type results, used with extreme rarity, reluctance and sadness, "Unable to determine".)

[khalidm3]

Assuming the initial problem was a positive direct antiglobulin test due to an autoantibody, most likely a panagglutinin, isn't there a good chance that the eluate will react with all panel cells due to the autoantibody, making it difficult to see the anti-D in there? If there isn't a clearcut specificity for anti-D, one might want to titer the eluate against a Rh+ cell and a Rh- cell in hopes of finding better a higher titer (or not) against the Rh+ cell.

This is, of course, to try to satisfy the insatiable blood banker's curiosity that we all possess. We want to know the answer to the problem! As was stated, you're not going to use the unit. (And I must admit that we do have a computer entry choice for blood type results, used with extreme rarity, reluctance and sadness, "Unable to determine".)

If panagglutinin, what will be the ICT (ABS)?