JAK2 detection accuracy

Posted by concernedmom34 @concernedmom34, Jul 17, 2023

Hello, my 22 year old son had a DVST about five months ago and following with all the testing his blood test showed less than 1% JAK2 was repeated and showed a 1% JAK2 He just had a bone marrow biopsy done, and it showed no detection of JAK2. This has all been very confusing and conflicting. His blood counts are in normal range. RBC has been slightly high at one blood draw. Before the bone marrow biopsy was done, he was told he had PV and now with the bone marrow biopsy results they are saying no evidence of an MPN. Just don’t know what to believe. Anyone have any input?

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sregiani | @sregiani | Jul 18, 2023

Is he seeing a specialist? IE: hematologist?

concernedmom34 | @concernedmom34 | Jul 18, 2023

In reply to @sregiani "Is he seeing a specialist? IE: hematologist?" + (show)

Yes he is

chella65 | @chella65 | Jul 19, 2023

This is a good place to learn. I am in an observation stage pending diagnosis. I'm confused too and have a list of questions for my hemotologist. I have set an appt to try to pin point. I am jak negative on blood test. Haven't had bone test yet. But my blood levels have been elevated for several years. Symptoms and elevated blood tests indicate either pv or secondary however they have examined my stomach and don't see anything major that would cause it. My hemo. Advised me they see about 20% Jak negatives as false results.
I think for me, is gathering information, talking with doctors and keep pressing for answers. This site is wonderful for connections for education.

Colleen Young, Connect Director | @colleenyoung | Jul 31, 2023

Hi @concernedmom34, have you had a chance to ask your son’s hematologist about the discrepancy in the findings between the blood testing and the bone marrow biopsy? If the biopsy ruled out MPN, what are your next steps?

concernedmom34 | @concernedmom34 | Jul 31, 2023

Ahhh if it were only so simple and direct. I have asked about the discrepancy and the hematologist wasnt quite sure why there weren’t the same results in blood test and BMB. Next step is that we are meeting with an MPN specialist on 8/25. I have sent her over the BMB results and she had 3 reasons that could explain the discrepancy 1)The jak2 mutation was in a mature progenitor cell that had a limited lifespan and so lived its life and then died.
2)His JAK2 cells are such a small percentage of cells they come up just at the level of detection in some studies and negative in others. The clinical implications of this are unknown, but probably insignificant.
3)The previous positives were lab error.

meghan213 | @meghan213 | Apr 19 2:19pm

Hi All,

I was curious about everyone's experience with a potential false positive JAK2? My husband had a positive JAK2 and we have the bone marrow biopsy scheduled. He had some more blood work done and a second JAK2 came back negative? Now, we are confused.

ger63 | @ger63 | Apr 20 7:44am

I have never had labs identifying jak2 only a bone marrow biopsy. It seems that would have more accuracy.

debhammel | @debhammel | Apr 20 8:21am

I had a blood test that included genetic testing that was positive for JAK2.

sregiani | @sregiani | Apr 20 9:17am

In reply to @meghan213 "Hi All, I was curious about everyone's experience with a potential false positive JAK2? My husband..." + (show)

Has anyone suggested DNA/genetic testing? That's what my Heme doc (an MPN specialist) did, and I was positive for Jak2.

nohrt4me | @nohrt4me | Apr 21 10:47am

In reply to @sregiani "Has anyone suggested DNA/genetic testing? That's what my Heme doc (an MPN specialist) did, and I..." + (show)

Yes, hemo scheduled JAK2 test. That was neg, but false negs happen, so she did the bone marrow biopsy looking for the telltale megakatyocytes that have an "elkhorn" shaped nucleus indicating ET.

Later, the CALR test became available, and I tested positive for that. Some insurance companies at that time (10 yrs ago) would only pay for CALR and MPL testing if you tested neg for JAK2. That's because all that testing is very expensive, and most ET patients have the JAK2 mutation.

So docs have to stagger these tests instead of doing them all at once to make sure that insurance will pay for them.

This drags out diagnosis and stresses out patients. But insurance companies aren't known for their big hearts ...