Initial investigations in the emergency department

Full blood count (FBC)

The suspicion of acute leukaemia will usually be raised by the FBC. Acute leukaemia normally causes leucocytosis, although a leucopaenic or pancytopaenic picture can be seen.

A haematological disorder is more likely if there are abnormal counts in at least two cell lines (e.g. anaemia with thrombocytopaenia), known as bicytopaenia. 

Blood film

If leukaemia is suspected, a blood film should be requested as the first-line investigation (although commonly this will already have been requested within the laboratory).

Acute leukaemia is characterised by the appearance of “blasts” (immature white blood cells) on the blood film. A diagnosis of acute leukaemia is made if blasts account for over 20% of the total white cell count in either peripheral blood or bone marrow3.

Occasionally, very few or no blasts will be seen within the peripheral blood; this does not rule out the presence of an underlying leukaemia within the bone marrow. A haematology referral can be made to consider a bone marrow test to investigate further.

Ed Uthman from Houston, TX, USA, CC BY 2.0 via Wikimedia Commons.

This image shows the typical appearance of a blast on a peripheral blood film.


A young female presents complaining of lethargy, malaise, oro-mucosal tingling and weight loss which have gradually worsened over 6 months. Her FBC is shown below.

Haemoglobin (g/L) 50     (115-165)
Mean Cell Volume (fl)

120     (80-100)

Platelets (109/L)

60      (150-400)

White cell count (109/L)

2         (4-11)

Neutrophil count (109/L)

1.2      (2-7.5)