Key Information

Appropriate Tests


The Full blood count specimen should be checked for clots and the blood film should be examined in all cases of thrombocytopenia to look for a cause and exclude ‘pseudo-thrombocytopenia (see below).

In vitro clumping of platelets can occur in the presence of EDTA, leading to spurious or ‘pseudo-thrombocytopenia'. Similarly, a partly clotted sample can lead to a falsely low result. A repeat platelet count on a specimen collected into citrate may confirm EDTA-associated clumping (the citrate platelet count normalising or being significantly higher).

See Table 1.

Full blood count, Blood film.

Bone marrow examination may be required if mechanism and/or cause is not obvious from clinical and/or blood film findings or if confirmation is required. This is omitted by some haematologists in younger otherwise healthy patients with isolated thrombocytopenia.

Reduced production


Isolated thrombocytopenia


  • Thiazide diuretics


  • Alcohol - has a direct marrow suppressant effect, as well as being associated with chronic liver disease and hypersplenism.

See Alcoholism

Congenital especially


  • Intra-uterine infection

See Neonatal bleeding under Bleeding disorders

  • Wiskott-Aldrich syndrome

See under Immunodeficiency

  • TAR syndrome

Amegakaryocytic thrombocytopenia with absent radii.

Increased destruction, margination, or loss


Immune - Autoimmune

See Immune thrombocytopenia



Lymphoproliferative disorder associated, especially

  • Chronic lymphocytic leukaemia
  • Lymphomas


Drug induced, especially

Platelet Ab testing 

  • Heparins

See Heparin-induced thrombocytopenia

  • Gold salts



Viral infection associated, especially

  • Infectious mononucleosis

Epstein-Barr virus serology and CMV serology may be indicated.

  • HIV infection

HIV serology should be checked in all cases of suspected immune thrombocytopenia.



Immune - Alloimmune


Neonatal thrombocytopenia

Platelet Ab testing and Platelet antigen testing of parents.

See also Neonatal bleeding

Post transfusion purpura

See transfusion reactions section in Blood transfusion.





Sepsis/Infection, especially


  • Septicaemia


  • Malaria



This is a common cause of thrombocytopenia. Abnormal Liver function tests may be helpful, however normal LFTs do not exclude the diagnosis. Imaging of the spleen by ultrasound or liver-spleen scan may be indicated.

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