To diagnose ALL, doctors will perform a physical exam of the patient and draw a sample of blood to do a complete blood count or CBC. There are various components in blood that generally fall within a certain range. For example, there are normally less than 10,000 white blood cells in a microliter of blood (a microliter is one-millionth of a liter). Doctors will examine the blood to see if the cells and components are within the normal range.
While an abnormal blood count is a key clue in diagnosing ALL, not every child with ALL will have an abnormal CBC. About 35 percent of ALL patients have a white blood cell count of more than 10,000 cells per microliter. Red blood cells and platelets are also counted in a CBC.
The diagnosis is confirmed by looking at the bone marrow directly. The marrow is found in the center of the bone, and a sample is retrieved using a needle. Leukemia is a rare disease and may not be immediately suspected, as many other illnesses have similar symptoms. Since the best outcome depends on starting treatment as early as possible, physicians may do a bone marrow test immediately if leukemia is suspected.
Cells from the marrow will be tested in a variety of ways and examined under a microscope to see if they have the distinguishing characteristics of ALL.
