Acute promyelocytic leukaemia (APL) tests for diagnosis

Ask your healthcare team to explain why you’re having a certain test and what the results mean.

Your doctors can diagnose APL with tests looking at your blood, bone marrow and genes.

A full blood count (FBC) measures the number of each type of cell in your blood – red blood cells, white blood cells and platelets.

If you are diagnosed with APL, you’ll have regular blood tests so your doctors can monitor your condition during and after treatment.

It’s not normally possible to diagnose APL with just a blood test. There may be leukaemia cells in your bone marrow that aren’t in your blood yet. Your bone marrow is a spongy tissue found inside some of your bones, where the body makes blood cells.

Your doctors will usually take a bone marrow sample (a biopsy) to look at under a microscope to check for leukaemia cells.

Find out more about having a bone marrow biopsy.

Although the results of a full blood count and bone marrow biopsy might suggest that you have APL, your doctors will need to run a few more tests on your blood and bone marrow samples to confirm a diagnosis.

These tests are looking at your genes, and are known as genetic tests. They look for specific changes in the chromosomes and genes in your abnormal blood cells – changes that you would expect to see in someone with APL.

It’s likely that you’ll start treatment before you’ve had all of these tests and before your diagnosis has been confirmed. This is because if there’s a chance that you have APL, you’ll need to start treatment straight away to lower the risk of bleeding.

Cytogenetics is the name for the study of chromosomes – the structures that hold your genes and DNA. are made up of your DNA and your genes.

Specialist doctors will look at chromosomes 15 and 17 in the abnormal cells. If these chromosomes are mixed up, this confirms a diagnosis of APL.

Your doctor will check cells from your bone marrow sample for the PML/RARA gene, because only people with APL have this gene. They’ll do this using a test called a polymerase chain reaction (PCR) test.

Immunophenotyping, also called flow cytometry, looks at the pattern of proteins on the surface of leukaemia cells. Together with the other tests, it helps your doctors to confirm whether you have APL or another type of leukaemia.

Several of the tests explained above can be used throughout treatment to monitor your condition. There are also some other tests you will need once you’re diagnosed:

APL can affect the blood clotting system in your body, and increase the risk of bleeding and blood clots. This means clotting tests are particularly important and you’ll have them regularly (at least once a day) in the early phases of your treatment.

Bleeding can become life-threatening if it’s not treated straight away, so your doctors will monitor you closely for this. You may need regular blood and platelet transfusions to lower your risk of bleeding.

You’ll have a general health check to assess how you’re likely to cope with the side effects of treatment. This will involve a range of tests to check your heart, liver and kidney function, and may include screening for HIV and hepatitis.