Chronic myeloid leukaemia (CML) is often first detected when a routine blood test is carried out during a routine check-up or when having blood tests for another condition. Other patients may present unwell to their GP or A&E department.

If you have CML, your blood count may show higher numbers than usual of white blood cells. You may also have higher numbers than usual of cells called platelets, and you may also be anaemic. CML has a distinctive appearance and the laboratory will examine an abnormal blood count under a microscope. Usually at this stage a diagnosis of CML is reasonably certain. If CML is suspected, the doctor will request another blood test called a PCR. This is to screen for the presence and quantity of the BCR-ABL1 fusion gene.

To confirm the diagnosis of CML and its phase, the haematology doctor or nurse will take a small sample of your bone marrow to examine under a microscope. This procedure is known as a bone marrow biopsy. A bone marrow biopsy is usually carried out under a local anaesthetic and sometimes gas and air or a mild sedative is also used.

The doctor or nurse will numb an area of skin at the back of your hip bone, before using a needle to remove the bone marrow sample. You may experience some bruising and discomfort for a few days afterwards. The procedure takes around 15 minutes or less to complete.

If CML is confirmed, the sample will be sent for PCR testing and quantification. It will also be examined for the presence of the Philadelphia chromosome and other chromosomal abnormalities.

CML is staged by finding out what phase the disease is in. There are three phases of CML: chronic, accelerated and blast phase. The main difference between the phases is the number of immature or blast cells present in the bone marrow. When the disease progresses, the patient has more blast cells present and more symptoms. Treatment at the accelerated phases can move you back into chronic phase.

As well as the phase of the disease, your doctor and clinical nurse specialist will look at your risk score. This is based on various factors at diagnosis, including your age, the size of your spleen and the numbers of various types of cells in the blood. Risk scores may also be used to determine which medication to give you.