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Genetic testing for thrombocythaemia (R406)

Thrombocythaemia is defined by a raised platelet count.

Background information

Most individuals are asymptomatic or have mild symptoms such as headache and dizziness, but may still have elevated risk of stroke.

Hereditary thrombocytosis results from heterozygous germline mutations affecting the thrombopoietin (TPO) receptor (MPL)/JAK2 signaling axis. Secondary causes such as an infection or iron deficiency and acquired JAK2 mutations are a far more common cause than germline mutations, and should be excluded before requesting this panel test (see M85 for somatic testing for exclusion of myeloproliferative neoplasms).

Testing strategy

Clinically affected probands

R406.1 – analysis for small variants in the small NGS gene panel.

Genes tested

Genes analysed are in accordance with the 'green' high evidence of clinical association gene list in panel app (see NGS gene panel).

Targetted analysis for known / previously reported familial variants

  • Presymptomatic testing in clinically unaffected family members at risk of inheriting a previously reported familial pathogenic variant (R242)
  • Diagnostic confirmation in individuals at risk of inheriting a previously reported familial pathogenic variant and clinically suspected of having the familial condition (R240)
  • Segregation studies in affected family members to aid variant interpretation (R375)

Target reporting times

Diagnostic test target reporting time is 42 days.

Presymptomatic, segregation and carrier testing target reporting time is 42 days, unless the test is urgent in which case the target is 21 days.

Prenatal diagnosis for familial variant target reporting time is 3 days.

For other reporting times, please see turnaround times.

Sample requirements and referral information

All referrals should be accompanied by a completed pre-referral form. See referral forms and specimen requirements and referring samples.

Clinical guidance and advice is available to referring clinicians from:

Dr Noémi Roy
Consultant Haematologist
John Radcliffe Hospital


Requesting specialties

  • Haematology
  • Clinical Genetics

Contact details

Haematology specific enquiries can also be emailed.


For other contact details, see contact us.

Price list for non NHSE referrals

Price list for rare disease services (pdf)

Last reviewed:23 April 2024