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significant antibody titers for Rh, Fya and K antibodies


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What are you all using as "significant" titers for antibodies to Rh, Duffy and K antigens?  I had an old reference that said to use 64 for anti-Fya, 8 for anti-K and we usually use 16 for Rh (all tube testing).  I see newer references suggesting using the same for anti-Fya as for Rh so thought I would check with this group for current practice/recommendations.

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As I am on the "wrong side of the pond", I'm not sure I should answer this, but I'll have a go!

We say a titre of 32 for anti-Fya and any Rh antibodies (but we perform concentrations on anti-D and anti-c, rather than titres, and for them we begin to worry if the anti-D levels go above 4IUmL-1 and anti-c lvels go above 7.5IUmL-1), however, I cannot recall seeing any real problems with anti-Fya below a titre of 128.

Anti-K (and other Kell-related antibodies) are a different kettle of fish.  After battling for years with poor correlation between anti-K titres and the severity of HDFN, and thinking it was poor titration technique, and then finding it wasn't, and finding out that it was more to do with how the antibody attacks the precursor red cells, we sort of gave up, and now we refer any pregnant women with anti-K to a foetal medicine unit for screening, just to be sure (unless cell free foetal DNA shows that the foetus lacks the KE L1 gene).

This is all based on British Committee for Standards in Haematology (BCSH): White J, Qureshi H, Massey E, Needs M, Byrne G, Daniels G, Allard S.  Guidelines for blood grouping and red cell antibody testing in pregnancy.  Transfusion Medicine 2016; 26: 246-263 (doi: 10:1111/tme.12299) and Royal College of Obstetricians and Gynaecologists (RCOG).  The management of women with red cell antibodies during pregnancy.  Green-top Guidelines No.65; May 2014.  https://www.rcog.org.uk/globalassets/documents/guidelines/rbc_gtg65.pdf.

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Hi Mabel,

It is performed on maternal peripheral blood by the International Blood Group Reference Laboratory in Filton.  They offer the service for the RHD gene, but also for the genes involved in the expression of the C, c, E, e and K antigens.

For any others, we would either have to rely on the father's phenotype (which may not be reliable), or on foetal cells from amniotic fluid (but we would almost certainly not do this, unless we are doing an invasive procedure for a different reason all together, because of the risk of foetal death).

All the best,

Malcolm

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