gel/ProVue and weak D

[yiams]

Blood Bankers, Has your facility established a cut off level or other guidelines for weak D patients? In other words if they Rh-type with gel (manual card or ProVue) as a 1+ reaction, do you consider the patient a weak/partial D as opposed to a patient who types 4+ with gel/ProVue would be a "straightforward" Rh-positive patient. A recent article in _Transfusion_ by Denomme, et al, "Rh discrepancies caused by variable reactivity of partial and weak D types with different serologic techniques" recommends that gel technology reactions <=2+ "... should be considered D- for the purpose of transfusion and Rh immune globulin prophylaxis." We would appreciate hearing how other users are handling this situation. Thank you.

[Kathy3171]

We use the cutoff of gel D <2+. These are reported as Rh negative and candidates for Rhogam. Until we have molecular testing for D, I don't think there is a way to truly determine weak/partial D's as some of these are capable of 3-4+ reactions.

[geekay]

Hi Kathy3171,

This is in reference to your reply.

I am very curious to know the origin of this "cut-off" value...

Any reference for this or was it by "the trial and error method" of the institution ?

If you can provide any references, I would be happy...

with best wishes...

[clai01]

BloodBankTalk

Our facility also adopted the same cutoff value for gel testing. The reference is from Dr. Judd's article, "Rh Discrepancies caused by variable reactivity of partial and weak D types with different serologic techniques".

[yiams]

Our pathologist just established the same cutoff limit of <=2+ this week. We used Judd's article and two others in addition to replies in this forum (there is another topic about Weak/Partial Ds that I found) and responses to Medlab list server. I would be more than happy to provide article citations ... except they are at work, I'm at home and I'm on vacation for two weeks! I'll be glad to dig them out for you when I return.

I need to read my own question before I post a response. I site a second of the three articles in my original post: Denomme, et. al. in a recent _Transfusion_. Again, that journal is at work so I can't say in which issue it appears. I believe it is a 2008 publication, if that's any help.

Edited June 7, 2008 by yiams
need to read my original question

[clai01]

It would be great if you could locate those articles. Our team is very interesting in reading the articles.

[Patty]

Do you use any cut offs for weak D when testing a cordblood sample to determine if Mom is RHIG candidate? Weak DAT's carry over to the D type/control making invalid. Do you consider baby RH Pos/Neg if reaction is less than 2+?

[Eoin]

Ortho BioVue have it in their blurb supplied with Gel cards. email me if you would like a copy. Your manufacturer should advise on this.

Cheers, eoin

[Kathy3171]

We referenced the same article by Dr Judd. As far as cord bloods that type <2+ by gel and/or are weak D positive, we have a canned comment that states the mother is a candidate for Rh prophylaxis but the infant is considered Rh negative for transfusions.

[Philip Thornton]

We use a cut-off of </= to 1+ and call these patients 'weak D' Rh POSITIVE. NOTE: Our policy specifically requires the use of Rh Negative Red Cells with patients classified as 'weak D' Rh positive because of the possibility of Anti-D production due to sensitization of the recipiant's partial antigen. This policy covers both tube and gel at our facility; tube because of the advent of strong reacting monoclonal reagents and gel because of the increased reaction sensitivity.

Cord and neonatal samples used for Rh immune globulin candidacy that display a weak or partial D are again called 'weak D' Rh positive but the mother is a candidate for RhoGam. This is also due to the possibility of Anti-D to a partial antigen.