Hi all,

We have a 28/40 pregnant patient, group O neg with an antibody that fits exactly with anti-D on our IAT panel but is negative in enzyme.

Previous sample reported by our reference lab as having non-specified antibody. Anti-D (and anti-E) could not be fully excluded.

No record of prophylaxis.

Any ideas?

Cheers,

Rich

Which proteolytic enzyme do you use?  I presume, as you are working in the Isle of Man, you use papain, but I just want to check.

Is the IAT assay exactly the same as the "enzyme" version (other than enzyme-treated cells) ?

Is the patient on IVIG?

Anti-Lw?

Don't know much about it - but I'm pretty sure it "looks" like a D - but then it's not................just googled and found this:

when testing for anti-LW, a key step is to use enzyme-treated cells to confirm its presence by observing a reduced or absent reaction compared to untreated cells

From a letter to the editor author Marcos Paulo Miola 2012 www.rbhh.org:

"The LW and Rh antigens are phenotypically related in such a way that
RhD+adult individuals express the anti-LW much more strongly than RhD-
individuals.

The expression of LW antigens may be depressed without any apparent reason during pregnancy and
in some hematologic diseases (Hodgkin’s, leukemias, lymphomas, sarcomas), regaining the normal or almost
normal expression after pregnancy and with remission of the diseases(4). The LW antibodies are not uncommon;
they may be produced without apparent exposure during the suppression periods of antigens, generally associated
with other antibodies. They are generally IgG, do not cause hemolysis, do not activate the complement system,
react to anti-human globulin (AHG) and present strong reactions with RhD+red cells and may or may not react with RhD-.

The LW antigens are resistant to papain and chloroquine treatment but are denatured by treatment
with 0.2m dithiothreitol (DTT)(5,6). To distinguish anti-LW from anti-D, red blood cells must be treated with
DTT (it denatures LW antigens but not Rh) and/or test with red cells from umbilical cord blood (as umbilical
cord blood presents a high expression of LW antigens, the anti-LW reacts well with RhD+and RhD-
cells)(6,7)."

Edited December 26, 2024Dec 26 by Texas Tea TMC

Hi and thanks for your replies. Sorry for not updating - i've been off work.

Our enzyme method is papainised cells tested using BioRad NaCl cards.

A follow-up sample reacted exactly the same for us but the reference lab report a unspecified antibody by IAT and enzyme IAT, don't say they cannot exclude anti-D or anti-E and require no further samples this pregnancy.

 

Rich

3 minutes ago, RichU said:

Hi and thanks for your replies. Sorry for not updating - i've been off work.

Our enzyme method is papainised cells tested using BioRad NaCl cards.

A follow-up sample reacted exactly the same for us but the reference lab report a unspecified antibody by IAT and enzyme IAT, don't say they cannot exclude anti-D or anti-E and require no further samples this pregnancy.

 

Rich

Hope you are okay.