Hereditary Thrombocythemia via the THPO Gene
Summary and Pricing 
Test Method
Exome Sequencing with CNV Detection
| Test Code | Test Copy Genes | Test CPT Code | Gene CPT Codes Copy CPT Code | Base Price | |
|---|---|---|---|---|---|
| 8655 | THPO | 81479 | 81479,81479 | $990 | Order Options and Pricing |
Pricing Comments
Our favored testing approach is exome based NextGen sequencing with CNV analysis. This will allow cost effective reflexing to PGxome or other exome based tests. However, if full gene Sanger sequencing is desired for STAT turnaround time, insurance, or other reasons, please see link below for Test Code, pricing, and turnaround time information. If the Sanger option is selected, CNV detection may be ordered through Test #600.
An additional 25% charge will be applied to STAT orders. STAT orders are prioritized throughout the testing process.
Click here for costs to reflex to whole PGxome (if original test is on PGxome Sequencing platform).
Click here for costs to reflex to whole PGnome (if original test is on PGnome Sequencing platform).
The Sanger Sequencing method for this test is NY State approved.
For Sanger Sequencing click here.Turnaround Time
3 weeks on average for standard orders or 2 weeks on average for STAT orders.
Please note: Once the testing process begins, an Estimated Report Date (ERD) range will be displayed in the portal. This is the most accurate prediction of when your report will be complete and may differ from the average TAT published on our website. About 85% of our tests will be reported within or before the ERD range. We will notify you of significant delays or holds which will impact the ERD. Learn more about turnaround times here.
Targeted Testing
For ordering sequencing of targeted known variants, go to our Targeted Variants page.
Clinical Features and Genetics
Clinical Features
Hereditary Thrombocythemia (HT) is a myeloproliferative condition characterized by chronic high platelet numbers. Most common symptoms include headache, lightheadedness, vision changes, numbness and burning pain in the hands and feet. Less common, but more severe, symptoms include abnormal clotting (thrombosis), and leukemic transformation. Alternatively, patients may also exhibit bleeding episodes leading to nosebleeds, bleeding gums, and/or gastrointestinal bleeds (Brière 2007; Teofili and Larocca 2011). This is thought to occur due to acquired von Willebrand disease (Michiels 1999). Diagnosis of HT typically involves exclusion of secondary thrombocythemia causes including chronic infection, iron deficiency, myeloproliferative malignancies, and acute blood loss. Germline mutation in the MPL gene or somatic mutation in the JAK2 gene have also been reported to cause thrombocythemia (Beer and Green 2009). Importantly, patients with JAK2 mutations are at heightened risks to develop myeloproliferative cancers whereas THPO and MPL mutations are typically non-neoplastic (Nielsen et al. 2011). Therefore, genetic testing can aid greatly in distinguishing HT from secondary thrombocythemia causes and predicting neoplastic risk through confirmation of the causative gene.
Genetics
There are three forms of HT. Type I is inherited in an autosomal dominant manner through mutation in the THPO gene. Type II is inherited in both autosomal dominant and recessive manners through mutation in the MPL gene. Type III is inherited or acquired somatically in an autosomal dominant manner with reduced penetrance through mutation in the JAK2 gene (Hussein et al 2013). Causative mutations within the THPO gene are primarily splice alterations and upstream substitutions impairing transcription (Hussein et al. 2013; Zhang et al. 2011; Wiestner et al. 1998). One missense mutation, p.Arg38Cys, leading to loss of protein function has also been reported (Dasouki et al. 2013). The THPO gene encodes the protein thrombopoietin with stimulates production of megakaryocytes and their differentiation into platelets.
Clinical Sensitivity - Sequencing with CNV PGxome
Mutations in the JAK2 and MPL genes account for ~50% and 4% of patient with HT respectively (Beer and Green 2009). Clinical sensitivity for HT cases due to THPO mutations is unknown at this time (Hussein et al. 2013). Analytical sensitivity should be high because all mutations reported are detectable by this method.
Testing Strategy
This test provides full coverage of all coding exons of the THPO gene plus 10 bases of flanking noncoding DNA in all available transcripts along with other non-coding regions in which pathogenic variants have been identified at PreventionGenetics or reported elsewhere. We define full coverage as >20X NGS reads or Sanger sequencing. PGnome panels typically provide slightly increased coverage over the PGxome equivalent. PGnome sequencing panels have the added benefit of additional analysis and reporting of deep intronic regions (where applicable).
Dependent on the sequencing backbone selected for this testing, discounted reflex testing to any other similar backbone-based test is available (i.e., PGxome panel to whole PGxome; PGnome panel to whole PGnome).
Indications for Test
Patients with chronically elevated platelet counts (>450 x 109/l) and proliferation in only the megakaryocyte lineage are primary indications for HT. Please refer to Tefferi et al. 2007 for a more detailed diagnostic guide for HT.
Patients with chronically elevated platelet counts (>450 x 109/l) and proliferation in only the megakaryocyte lineage are primary indications for HT. Please refer to Tefferi et al. 2007 for a more detailed diagnostic guide for HT.
Gene
| Official Gene Symbol | OMIM ID |
|---|---|
| THPO | 600044 |
| Inheritance | Abbreviation |
|---|---|
| Autosomal Dominant | AD |
| Autosomal Recessive | AR |
| X-Linked | XL |
| Mitochondrial | MT |
Disease
| Name | Inheritance | OMIM ID |
|---|---|---|
| Essential Thrombocythemia | AD | 187950 |
Citations
- Beer PA, Green AR. 2009. Pathogenesis and management of essential thrombocythemia. Hematology Am Soc Hematol Educ Program 621–628. PubMed ID: 20008247
- Brière JB. 2007. Essential thrombocythemia. Orphanet J Rare Dis 2: 1–17. PubMed ID: 17210076
- Dasouki MJ, Rafi SK, Olm-Shipman AJ, Wilson NR, Abhyankar S, Ganter B, Furness LM, Fang J, Calado RT, Saadi I. 2013. Exome sequencing reveals a thrombopoietin ligand mutation in a Micronesian family with autosomal recessive aplastic anemia. Blood 122: 3440–3449. PubMed ID: 24085763
- Hussein K, Granot G, Shpilberg O, Kreipe H. 2013. Clinical utility gene card for: familial polycythaemia vera. European Journal of Human Genetics 21: PubMed ID: 23032109
- Hussein K, Percy M, McMullin MF, Schwarz J, Schnittger S, Porret N, Martinez-Aviles LM, Paricio BB, Giraudier S, Skoda R, Lippert E, Hermouet S, et al. 2014. Clinical utility gene card for: Hereditary thrombocythemia. European Journal of Human Genetics 22: PubMed ID: 23736217
- Michiels JJ. 1999. Acquired von Willebrand disease due to increasing platelet count can readily explain the paradox of thrombosis and bleeding in thrombocythemia. Clin. Appl. Thromb. Hemost. 5: 147–151. PubMed ID: 10725999
- Nielsen C, Birgens HS, Nordestgaard BG, Kjaer L, Bojesen SE. 2011. The JAK2 V617F somatic mutation, mortality and cancer risk in the general population. Haematologica 96: 450–453. PubMed ID: 21160067
- Tefferi A, Thiele J, Orazi A, Kvasnicka HM, Barbui T, Hanson CA, Barosi G, Verstovsek S, Birgegard G, Mesa R, Reilly JT, Gisslinger H, et al. 2007. Proposals and rationale for revision of the World Health Organization diagnostic criteria for polycythemia vera, essential thrombocythemia, and primary myelofibrosis: recommendations from an ad hoc international expert panel. Blood 110: 1092–1097. PubMed ID: 17488875
- Teofili L, Larocca LM. 2011. Advances in understanding the pathogenesis of familial thrombocythaemia: Review. British Journal of Haematology 152: 701–712. PubMed ID: 21303356
- Wiestner A, Schlemper RJ, Maas AP van der, Skoda RC. 1998. An activating splice donor mutation in the thrombopoietin gene causes hereditary thrombocythaemia. Nat. Genet. 18: 49–52. PubMed ID: 9425899
- Zhang B, Ng D, Jones C, Oh ST, Nolan GP, Salehi S, Wong W, Zehnder JL, Gotlib J. 2011. A novel splice donor mutation in the thrombopoietin gene leads to exon 2 skipping in a Filipino family with hereditary thrombocythemia. Blood 118: 6988–6990. PubMed ID: 22194398
Ordering/Specimens
Ordering Options
We offer several options when ordering sequencing tests. For more information on these options, see our Ordering Instructions page. To view available options, click on the Order Options button within the test description.
myPrevent - Online Ordering
- The test can be added to your online orders in the Summary and Pricing section.
- Once the test has been added log in to myPrevent to fill out an online requisition form.
- PGnome sequencing panels can be ordered via the myPrevent portal only at this time.
Requisition Form
- A completed requisition form must accompany all specimens.
- Billing information along with specimen and shipping instructions are within the requisition form.
- All testing must be ordered by a qualified healthcare provider.
For Requisition Forms, visit our Forms page
If ordering a Duo or Trio test, the proband and all comparator samples are required to initiate testing. If we do not receive all required samples for the test ordered within 21 days, we will convert the order to the most effective testing strategy with the samples available. Prior authorization and/or billing in place may be impacted by a change in test code.
Specimen Types
Specimen Requirements and Shipping Details
PGxome (Exome) Sequencing Panel
PGnome (Genome) Sequencing Panel
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ORDER OPTIONS
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2) Select Additional Test Options
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