Your child will need several tests to diagnose AML. Some will be repeated on a regular basis to help doctors monitor their progress.
There are different types of AML, so it’s really important that you know your child’s exact diagnosis.
Tests to diagnose AML
AML is diagnosed by tests on blood, bone marrow and cerebrospinal fluid (CSF), the fluid in which the brain and spinal cord are bathed. It will usually take a few days for all the diagnostic tests to be completed, but there’s rarely any doubt about a diagnosis of childhood AML.
You can ask, at any time, for an explanation of why a particular test is being done and what the results mean.
Blood tests can provide doctors with a lot of information about your child’s condition.
The main blood test is called a full blood count. It measures the number and type of red blood cells, white blood cells and platelets, and will show if there are any leukaemia cells present. You may also hear these terms:
- flow cytometry: this studies the physical and chemical characteristics of blood as it passes through laser beams; it can measure the number and type of cells in a sample
- morphology (or morphologic analysis): this refers to what the cancerous cells look like under the microscope.
Bone marrow sample
Blood cells are made in the bone marrow, so there may be leukaemia cells there even if the blood sample is normal. A bone marrow sample can confirm a diagnosis and show what type of AML your child has.
Using a needle, a small amount of bone marrow is taken (aspirated) from the pelvis. This is usually done under general anaesthetic.
Doctors may also remove a small core of bone marrow (trephine biopsy) to examine the structure of the bone marrow, the number and type of blood cells and, if present, leukaemia cells.
Once doctors have the blood and bone marrow samples they need, they’ll do a range of laboratory tests to find out the type of AML your child has and the best treatment for it. You may hear these terms being mentioned:
- cytogenetic analysis tests: these look for any abnormality in the chromosomes in your child’s leukaemia cells
- molecular tests: these look for specific genetic faults which can give an indication of how likely the leukaemia will respond to treatment – they can also be used for monitoring response to treatment and can sometimes give an indication that the leukaemia may respond to newer drugs
- immunophenotyping: this looks for the proteins produced by some leukaemia cells – on the aspirate this is done by flow cytometry.
This procedure (sometimes called a spinal tap) is done to look for leukaemia cells in the cerebrospinal fluid (CSF). This is the fluid that surrounds your brain and spinal cord. A sample of CSF is taken through a needle inserted into the spinal column, in the space below the spinal cord. The procedure is usually done under a general anaesthetic.
Minimal residual disease monitoring (MRD)
This test is becoming more common for AML. Your child will have one when they’re first diagnosed, then others during their treatment, so doctors can measure how well they’re responding to it.
The test looks at a bone marrow sample and detects how many leukaemia cells remain in the bone marrow after treatment. When your doctors look at blood cells through a microscope, the lowest number of leukaemia cells they can detect is about one leukaemia cell in 20 normal cells. The MRD test is much more sensitive and can detect leukaemia cells at levels as low as one leukaemia cell in 100,000 normal cells.
The results of the MRD test will help your doctors decide how much treatment your child needs, and it may help them to predict how successful their whole treatment programme will be.