Intended for healthcare professionals

Practice Rational Testing

Investigating an incidental finding of thrombocytopenia

BMJ 2013; 346 doi: (Published 11 January 2013) Cite this as: BMJ 2013;346:f11
  1. Charlotte Bradbury, specialist registrar in haematology1,
  2. Jim Murray, consultant haematologist1
  1. 1University Hospital Birmingham, Birmingham B15 2PR, UK
  1. Correspondence to: J Murray jim.murray{at}

This article discusses the most common causes of incidental thrombocytopenia and provides advice on the relevant investigations

Learning points

  • When thrombocytopenia is found, repeat the blood count and request a blood film. This will confirm whether thrombocytopenia is genuine and will help direct subsequent investigations

  • Take a careful drug history, ask about risk factors for HIV and hepatitis C, and assess for features of liver disease

  • If the patient is well, has no abnormal clinical findings, and has isolated thrombocytopenia with no other abnormalities on blood count or film, immune thrombocytopenia is the most likely cause

  • The risk of bleeding is not based on the platelet count alone; also consider age, comorbidity, mandated anticoagulation, risk of trauma, and any need for surgery

An asymptomatic 64 year old woman presented to her general practitioner with fatigue and weight gain. Full blood count indices were haemoglobin 125 g/L (reference range 115-165), mean cell volume 90 fL (80-99; 1fL=1 µm3), platelets 54×109/L (150-400), white cell count 6.3×109/L (4-11), and neutrophils 4.8×109/L (2-7.5). A blood film confirmed the low platelet count but was otherwise normal.

What is the next investigation?

Thrombocytopenia may result from impaired production of platelets (for example, as a result of marrow dysfunction), increased destruction (immune or non-immune), abnormal distribution, or a combination thereof. Table 1 lists common causes and examples.

View this table:
Table 1

  Common causes of thrombocytopenia

If isolated thrombocytopenia is picked up incidentally in an apparently asymptomatic patient with no relevant drug treatment and a normal blood film, the diagnosis is usually immune thrombocytopenia (ITP).1 2 No accurate data on the relative frequencies of different causes of thrombocytopenia are available in the literature, although there is now an international paediatric and adult registry.3 ITP is an acquired disorder characterised by an isolated thrombocytopenia of less than 100×109 …

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