Secondary Thrombocytosis Workup

Updated: Dec 01, 2020
  • Author: Devapiran Jaishankar, MBBS; Chief Editor: Srikanth Nagalla, MD, MS, FACP  more...
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Approach Considerations

The laboratory workup in suspected cases of secondary thrombocytosis (reactive thrombocytosis) includes the following:

  • Erythrocyte sedimentation rate (ESR), C-reactive protein (CRP)
  • Cytogenetic analysis
  • Leukocyte alkaline phosphatase
  • Vitamin B12
  • Antinuclear antibody (ANA), rheumatoid factor (RF)
  • Iron studies (serum iron, total iron-binding capacity [TIBC], serum ferritin)
  • Peripheral blood smear review

If the clinical presentation does not clearly differentiate between primary (clonal) and secondary thrombocytosis, further tests may be indicated to exclude or confirm a diagnosis of disorders that cause clonal thrombocytosis, as follows:

  • Cytogenetic studies: The presence of the Philadelphia chromosome (Ph) found in chronic myelogenous leukemia (CML) may also be identified using reverse transcriptase polymerase chain reaction (RT-PCR) to identify the bcr-abl fusion transcript or by using Southern blot analysis for identification of bcr-abl genomic rearrangements.

Essential thrombocythemia is a diagnosis of exclusion. The 2017 World Health Organization (WHO) diagnostic criteria for essential thrombocythemia include 4 major and 1 minor criteria. [4]  Diagnosis requires meeting all 4 major criteria or the first 3 major criteria and the minor criterion. The major criteria are as follows::

  1. Platelet count ≥450 × 109/L
  2. Bone marrow biopsy showing megakaryocyte lineage with increased numbers of enlarged, mature megakaryocytes with no significant increase in neutrophil granulopoiesis or erythropoiesis and, rarely, minor reticulin fibers.
  3. Not meeting WHO criteria for CML, polycythemia vera (PV), primary myelofibrosis, myelodysplastic syndromes, or other myeloid neoplasms.
  4. Presence of JAK2CALR or MPL mutation

The minor criterion is the presence of a clonal marker or absence of evidence of reactive thrombocytosis (eg, infection, inflammation, iron deficiency anemia).