Leukemia must be distinguished from reactive leukocytoses and from cytopenias such as aplastic anemia. For instance, in a child, acute lymphoblastic leukemia (ALL) must be distinguished from a viral lymphocytosis.

The type of leukemia has prognostic and theraputic significance. Of the acute leukemias, ALL has a much better prognosis than acute myeloblastic leukemia (AML).

The diagnosis and clasification of leukemia is accomplished largely through the laboratory examination of peripheral blood and bone marrow.

The principle studies include:

• Morphology
  • peripheral blood smear
  • bone marrow aspirate & biopsy
• Cytochemistry
• Genetic analyses-chromosomal and molecular
• Immunology

The initial laboratory evaluation of a suspected leukemia requires a complete blood count (CBC) including a platelet count and an examination of a peripheral blood smear.

Although the white blood cell count (WBCc) is typically thought of as being greatly increased in leukemia, the WBCc is really highly variable, ranging from severe leukopenia to extreme leukocytosis.

The platelet count is generally decreased in acute leukemias, but is often normal in chronic leukemias.

The hematocrit and hemoglobin usually reflect a normocytic/normochromic anemia.