Childhood leukemia is diagnosed in a variety of ways.The diagnostic procedures confirm the presence of leukaemia cells, its type, and the extent it has spread.The diagnostic procedures are similar for the different types of leukaemia. The following tests and procedures may be used to diagnose the disease.

Medical History and Physical Examination

A Physical examination is done by a doctor who will look for any enlarged lymph nodes, signs of an enlarged spleen or liver, areas of bleeding or bruising, or possible signs of infection.
It is important to let the doctor know about the medical history of the child and also about any possible exposure of the family to various risk factors associated with the disease including the family history of cancer.

Blood Test

A Complete Blood Count(CBC) is done to measure the size, number, and maturity of different blood cells in blood. Blood tests may include blood chemistry, evaluation of liver and kidney functions, and genetic studies.

Bone Marrow Aspiration and Biopsy

Bone-marrow aspiration and biopsy is done to look for and collect leukaemia cells. In aspiration, a fluid sample is removed from the marrow. In biopsy, bone marrow cells are removed. Usually both procedures are performed at the same time and used together to help with diagnosis and is also repeated later to find out if the leukaemia is responding to medication or not.

Lumbar Puncture

Lumbar Puncture (Spinal Tap) is done to look for leukaemia cells in the cerebral spinal fluid that bathes the child's brain and spinal cord. A special needle is inserted between the bones of the lower back area of the spinal cord. A small amount of cerebral spinal fluid is sent for testing to determine if leukaemia cells are present.
Lumbar punctures might also be used to give chemotherapy drugs into the cerebral spinal fluid to prevent or treat the spread of leukaemia to the spinal cord and brain.

Immunophenotyping/Cytogenetic Analysis

Tests called immunophenotyping and cytogenetic analysis are performed on the cancer cells to further determine the exact type of leukaemia.

Chest x-rays

A chest x-ray can help detect an enlarged thymus or lymph nodes in the chest. If the test result is abnormal, a CT Scan of the chest may be done to get a more detailed view.