January 8, 2026

In the diagnostic workup for suspected myeloproliferative neoplasms, the exact pathway depends upon presenting signs and symptoms. As of January 6, 2026, Warde Medical Laboratory offers two new tests useful in confirming or excluding a number of disease states including polycythemia vera (PV), essential thrombocytosis (ET), primary myelofibrosis (PMF), chronic neutrophilic leukemia (CNL), and other related disorders.

JAK2 V617F mutation testing by PCR (JAK2Q) is often the best starting point for these workups, and a quantitative assay has already been available at Warde. This remains the best option for evaluation of mild erythrocytosis or moderate erythrocytosis with likely secondary etiology.

For high platelet count, splenomegaly, or other findings suggesting  ET or PMF, Warde now offers JAK2X, which reflexes from negative JAK2 V617F PCR result to follow-up testing of mutations in CALR, MPL, CSF3R, and JAK2 exon 12 (by NGS).

CALR and MPL mutations account for the majority of ET and PMF cases that are negative for JAK2 V617F. If JAK2 V617F test shows positivity, no reflex testing is performed and the only charge is for JAK2 V617F quantitative result. CSF3R mutations are responsible for many cases of CNL, and is therefore also included in the panel.

Rare cases of PV are driven not by JAK2 V617F, but instead by mutations in exon 12; for this reason JAK2 exon 12 is included in the NGS panel as well. Note that patients with a low probability of PV may be better served with JAK2Q rather than JAK2X, based on the reflex logic (negative result causes additional testing and cost), whereas cases with higher index of suspicion for PV would benefit from JAK2X to evaluate exon 12 when the V617F mutation is absent.

For patients who have already had a JAK2 V617F test, and other patients for whom reflexing may not be the best option, the NGS portion of this reflex is available as a standalone test (FMPN) evaluating CALR, MPL, CSF3R, JAK2 exon 12, (and JAK2 V617F as well).

Given that FMPN does evaluate JAK2 V617F status, why is the reflex test JAK2X a better option than FMPN for many patients?

1. When JAK2 V617F is positive, the cost of the test (PCR alone) is significantly less than the cost of the FMPN NGS panel.
2. Sometimes, a clinician may feel there is diagnostic benefit to having quantification of JAK2 V617F mutation burden.

The best candidates for proceeding directly to FMPN testing are those with known JAK2 V617F negativity, as the cost is lower (because PCR is not performed first). Diagnostically, there is little risk in ordering FMPN instead of the reflex, since JAK2 V617F will be evaluated.

Warde also offers a comprehensive NGS panel for hematologic malignancies (MNGS): all mutations discussed above are included, along with nearly 100 other loci. This is occasionally an appropriate first-line investigation in myeloproliferation. Note that when FMPN has already been performed on a patient, it is possible for you to add-on a full MNGS study to the same sample: clear communication with a Warde director or staff member is necessary for this option. The total cost of testing for those cases will be just the price of MNGS (additional charge of only the difference between MNGS and FMPN).  

Here are the full names for these offerings (as the Warde test code may not appear on your menu):

JAK2Q: JAK2 GENE, (V617F) MUTATION, QUANTITATIVE, PCR
JAK2X: JAK2 WITH REFLEX TO NGS FOR EX12/CALR/MPL
FMPN: FOCUSED MYELOPROLIFERATIVE NEOPLASM PANEL