• Blood sample: To diagnose AML, a doctor will do blood tests to count the number of white blood cells and see if they look abnormal under the microscope. Special tests called immunophenotyping or flow cytometry and cytochemistry are sometimes used to distinguish AML from other types of leukaemia and determine the exact subtype of AML ^?2?.
• Bone marrow sample:

  These two procedures are similar and often done simultaneously to evaluate the bone marrow, which is the fatty, spongy tissue found inside larger bones. Bone marrow has both a liquid and a solid part. A bone marrow aspiration takes a sample of the fluid using a needle. A bone marrow biopsy removes a small quantity of solid tissue using a needle.

  A pathologist then reviews the samples in a lab. Pelvic bone located by the hip is a common site for bone marrow aspiration and biopsy. Doctors generally give a medication called "anaesthesia" beforehand to numb the area. Anaesthesia is a medication that blocks the awareness of pain.

• Molecular and genetic testing: Your doctor may also recommend running laboratory tests to identify specific genes, proteins, and other factors involved in leukaemia. Examining the genes in the leukaemia cells is essential because the cause of AML can be due to the buildup of mistakes (mutations) in the cell's genes. In addition to it, identifying these mutations helps diagnose the specific subtype of AML and decide treatment options. Additionally, the results of those tests can help us monitor how well the treatment is working. Mentioned below are the more common molecular or genetic tests used for AML ^?3?.

• Spinal fluid: This procedure is also called a lumbar puncture or spinal tap. In this method, the cerebrospinal fluid (CSF) is removed from the spinal cord. This procedure is only recommended when there are signs of acute myeloid leukaemia spreading to the CNS system. Also, the lumbar puncture procedure is used as a treatment procedure to deliver chemotherapy drugs.

• Cytochemical and immunohistochemical tests: Cytochemical and immunohistochemical tests are laboratory tests that help to determine the exact subtype of AML. Furthermore, in cytochemical tests, a specific dye stains the different types of leukaemia cells differently based on the chemicals in the cells. For AML, immunohistochemical tests and a test known as flow cytometry help to find markers on the surface of the leukaemia cells. The different subtypes of leukaemia have different and unique combinations of cell surface markers.

• Cytogenetics: Cytogenetics is a way to look at a cell's chromosomes through a microscope to analyze the number, shape, size, and arrangement of the chromosomes to find genetic changes in leukaemia cells. Sometimes, a chromosome part breaks off and attaches to another chromosome, known as translocation. Other times, part of a chromosome is missing, known as deletion. A chromosome can be made more than once, most often called trisomy. The cause of some leukaemia subtypes may be chromosome translocations, deletions, or trisomies ^?4?.

  Knowing if specific translocations may help doctors determine the AML subtype and plan the best treatment. Fluorescence-in-situ-hybridization (FISH) is also one of the ways to detect chromosome changes in cancer cells. It also helps diagnose and determine the subtype of leukaemia. This is done on tissue removed in aspiration or biopsy.

  The molecular genetics of leukaemia cells can also determine if a person needs more or less chemotherapy or bone marrow/stem cell transplantation. This type of testing looks for minute genetic mutations, called sub-microscopic mutations.

Lab tests

• Complete blood count (CBC) & Peripheral blood smear: TheCBC test measures the amounts of different cells in the blood, such as the RBCs, WBCs, and platelets. Peripheral blood smear helps in identifying the changes in the numbers and the appearance of different types of blood cells.
• Routine cell exams under microscope: Samples of blood, bone marrow, or CSF are observed under a microscope to look at and classify the WBC according to their size, shape, and other traits.
• Cytochemistry: The cells in the sample are exposed to chemical stains (dyes) that react with only some types of leukaemia cells. These stains induce colour changes that can be observed under a microscope, to differentiate.
• Flow cytometry & Immunohistochemistry: The cells in the samples are treated with antibodies (proteins), that fasten to specific proteins on cells. These methods are used for immunophenotyping leukaemia cells, which helps in the classification of acute myeloid leukaemia. In Flow cytometry, the cells are observed under a microscope whereas special equipment is used in Immunohistochemistry.
• Chromosome tests: These tests observe the chromosomes. Cytogenetics test is a type of chromosome test, where the chromosomes are observed under microsome to observe changes in chromosomes, which include deletion, inversion, addition or duplication, and translocation. Fluorescent in situ hybridization (FISH) observes specific changes in certain parts of the DNA with the help of dyes. Polymerase chain reaction (PCR) is a sensitive test that can also find the changes that are too small to be observed under a microscope. It helps find gene changes that are in only a few cells, making it good for finding small numbers of leukaemia cells in a sample, it is prescribed after or during the treatment to evaluate the treatment and make any further changes in the treatment.

Imaging tests

• X-ray: A regular X-ray is suggested if any infection to other organs is suspected.
• Computed tomography (CT) scan: Generally CT scans use X-rays to get the cross-sectional image of the focused organ. Sometimes CT scan can also be used to guide a biopsy needle if the abscess is suspected. Also, sometimes a PET scan is used along with a CT scan for more precise diagnosis as PET use radioactive sugars to capture a picture of the regions of high radioactivity as the cancer cells absorb large amounts of sugar, then a CT scan is used to observe the region more detailed.
• Magnetic resonance imaging (MRI) scan: MRI scan gives precise images of the soft tissues like the CT scan, but instead of using x-rays like for CT scan, radio waves are used for MRI scan.
• Ultrasound: This procedure uses sound waves to make an image of the internal organs or masses. Ultrasound can be used to observe lymph nodes near the surface of the body or to look inside your abdomen for enlarged lymph nodes or organs such as the liver, spleen, and kidneys. Also, it is sometimes used to guide the needle inside swollen or enlarged lymph nodes for a biopsy.

If you are diagnosed with acute myeloid leukaemia (AML), your oncologist/ doctor will discuss the treatment options that can be based on the acute myeloid leukaemia subtype, other prognostic factors, age and your overall health status.

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Reference:

1. Arber DA, Erba HP. Diagnosis and Treatment of Patients With Acute Myeloid Leukemia With Myelodysplasia-Related Changes (AML-MRC). Am J Clin Pathol. 2020 Nov 4;154(6):731-741. doi: 10.1093/ajcp/aqaa107. PMID: 32864703; PMCID: PMC7610263.