BMB JAK2 versus Blood JAK2?

[Paul123456]

Had a BMB and Blood test on same day, my BMB % JAK2 was 23% whereas my Blood JAK2 % was 30%.

Can anyone please explain the difference? Which one is the most relevant? We’ve debated whether Blood JAK2 % is measured relative to Neutrophils but I can’t see much correlation with my Blood JAK2 results

Thanks

[EPguy]

I had BMB=19% and blood = 14% at Dx so the other way from yours. I've tried to learn more esp how blood VAF is measured. No luck on the details, best I can tell is the methods used for blood differ and have changed over the years. It seems many different cells and even maybe plasma have been used to measure VAF.

We discussed this in:

healthunlocked.com/mpnvoice...

Here is a part of that one:

"More recently we get alleles via "ddPCR" and it seems they use "whole blood" rather than certain parts. I also saw a modern report using just serum (the liquid part).

"DNA was obtained out of 400 μL of whole blood"

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There is a report that's been posted a few times that found the two ways giving same results. You and I can say not necessarily so.

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I asked my specialist about this, he said one is not more relevant than the other, but comparing the same type does matter. We will use blood via the same lab to compare. I would think BMB is the standard, but apparently not.

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Maybe no relevance, but for SCT they now use blood from the donor, it used to require marrow. Maybe VAF is also evolving to favor the blood route as the methods got better.

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Has your VAF (by the same method) changed recently?

[Paul123456 in reply to EPguy]

Yes nothing changed that I’m aware of.

Intuitively I wondered whether marrow would be in advance of blood since the source but your results and gvibes don’t correlate

Best Paul

[gvibes]

Hi Paul,

At diagnosis at the end of 2020, my blood had 5% VAF and shortly thereafter bone marrow aspirate found 35.3 % VAF. I have one of the less common JAK2 exon 12 mutations (negative for v617f). Because this testing requires the 75 gene panel, (which is expensive and requires battles with the health insurance co), I have only done this once. I initially thought there was some kind of lab error, but now believe its real. It kind of makes sense that the bone marrow aspirate might be higher than blood as its where the mutated cells are made and somehow the blood could be diluted (pure speculation). Yours shows the opposite pattern. I have an appt with my MPN doctor next month and I will ask him. I have been on interferon (Pegasys) for almost 2 years so curious as to the current values and any trends. I will share any information I find out.

Take care.

[EPguy in reply to gvibes]

That is a very large difference, I think I've seen your prior post on it. It seems blood measuring methods are still evolving and exon 12 is even less settled there.