Hello group,

Just wanted to ask if anyone else has seen a patient with anti-Vel that is compatible with Vel variant units is LISS and Gel but <1+ incompatible with PEG. Which in this case is the same reactions that we get when RBCs from a known Vel negative unit are crossmatched.

Thanks for the feedback.

Anti-Vel is such a nasty antibody, I would give units that are known to be molecularly tested (SMIM-1 Negative), unless the cross-match is performed by 2-stage IAT with monospecific anti-C3d on a clotted sample, as it is renowned for complement activation, even when virtually undetectable by normal serological techniques - not that I want to be sensationalist!

I can't really explain your serological findings, but I agree with Malcolm's sentiment: "That stuff'll kill ya!" Anti-Vel is notoriously slippery and infamously dangerous.

Without a more detailed look at your results, I see a few remote possibilities:

1. The anti-Vel may have an IgM component that doesn't like the Gel, but does like the PEG test

2. There's possibly something underlying the anti-Vel, hence the "extra" reactivity

3. The unit you crossmatched is not actually Vel-, but another member of the Vel variant club

I like explanation one very much exlimey.  Very many of the examples of anti-Vel I have encountered (and I have seen many, as I was working at the BGRL in London in the mid to late 1970's when Dr Bertil Cedegren was studying the percentage of Vel Negative donors in the Swedish population) had a high concentration of IgM, and a low concentration of IgG.

1 hour ago, Malcolm Needs said:

I like explanation one very much exlimey.  Very many of the examples of anti-Vel I have encountered (and I have seen many, as I was working at the BGRL in London in the mid to late 1970's when Dr Bertil Cedegren was studying the percentage of Vel Negative donors in the Swedish population) had a high concentration of IgM, and a low concentration of IgG.

Exactly. And very likely to cause in vitro hemolysis in appropriate test systems (not to mention in vivo hemolyis). I remember doing many 2-stage EDTA tests, using fresh complement and poly AHG. Good times.

I think I may have met Dr. Cedergren when I was working at the BGRL in Oxford during the late 1980's.

He was a delightful chap.

Thank you very much for the responses!

On 3/5/2020 at 3:59 PM, Malcolm Needs said:

Anti-Vel is such a nasty antibody, I would give units that are known to be molecularly tested (SMIM-1 Negative), unless the cross-match is performed by 2-stage IAT with monospecific anti-C3d on a clotted sample, as it is renowned for complement activation, even when virtually undetectable by normal serological techniques - not that I want to be sensationalist!

Reminds me of a recent forum post I read elsewhere about someone who wanted to give a patient with an anti-Vel phenotypically negative units from family members that actually were still genetically variant. The consensus was molecular negative donor units only!