Table 2.

Causes of thrombocytosis (adapted.from [18, 19])

Primary or clonal	Secondary or reactive	Artefactual or spurious
Essential thrombocytosis	Acute blood loss	Erythrocyte fragments
Polycythaemia vera	Trauma	Schistocytes
Primary myelofibrosis	Surgery	Microcytosis
Familial/hereditary thrombocytosis	Infectious diseases	Spherocytosis
Chromosome 5q-deletion syndrome	Iron deficiency	Cryoglobulinaemia
Chronic myeloid leukaemia	Asplenia	Neoplastic fragments
Chronic myelomonocytic leukaemia	Malignancy	Bacteria
Atypical chronic myeloid leukaemia	Chronic inflammationa	Fungi
Myelodysplastic syndrome	Haemolysis	Lipid dropletsc
Unclassifiable myeloproliferative neoplasms	Allergic reactions	–
RARS‑T	Exercise	–
POEMS syndrome	Medicationb	–

RARS‑T refractory anaemia with ringed sideroblasts associated with marked thrombocytosis.

POEMS acronym for a rare blood disorder with the following signs/symptoms: polyneuropathy, organomegaly, endocrinopathy/oedema, monoclonal protein, skin changes

^aFor example, rheumatic diseases

^bFor example, low-molecular-weight heparin, ceftazidime, clozapine, gemcitabine, non-steroidal anti-inflammatory drugs and steroids

^cNotably when samples are taken shortly after a meal