High platelets (platelets >450 x 10^9 /L)

South Tees Hospitals NHS Foundation Trust

Definition/Description

A high platelet count is most often reactive, in the same way that a plasma viscosity, CRP or ESR may be elevated. If there is no obvious reactive cause then other possibilities should be considered.

Red Flag Symptoms

None provided

Guidelines on Management

Differential diagnosis:

Physiological - post-splenectomy
Reactive to infection, inflammation or malignancy*. May be associated with neutrophil leucocytosis and anaemia of chronic disease. *Thrombocytosis can be a marker for cancer, including lung, endometrial, gastric, oesophageal or colorectal.
In response to blood loss or trauma. If chronic blood loss may also see iron deficiency anaemia.
Related to a myeloproliferative disorder, e.g. essential thrombocythaemia (isolated thrombocytosis); polycythaemia vera (also raised haematocrit); or proliferative phase myelofibrosis (splenomegaly often a feature). Most patients will have a JAK2, CALR or MPL mutation.

Examination:

Examine for hepatomegaly or splenomegaly.

Baseline investigations:

FBC, blood film, U+E, LFT, calcium, inflammatory markers
Ferritin if anaemia (may be falsely elevated if raised inflammatory markers)
Chest x-ray
Other investigations depending on history / examination and clinical suspicion

Referral Criteria/Information

Referral:

Consider haematology referral if:

Persistently raised platelets (>450x10⁹ /L) with no obvious underlying cause / normal inflammatory markers.
Splenomegaly or blood film suggestion of a primary bone marrow disorder.

If a raised platelet count is part of an unexplained inflammatory condition (e.g. raised WCC, anaemia of chronic disease, raised inflammatory markers) then consider referral to General Medicine.