First suspicion of CML comes when we laboratory tests show high levels of leukocytes and presence of immature leukocytes in the blood. However, if the patient also has some of the symptoms mentioned above, complementary tests should be conducted to confirm this suspicion.

Complementary tests include:

• Bone marrow aspiration: involves taking a sample of bone marrow (while under local or general anesthesia) or a biopsy; during a biopsy, a small sample of bone is taken following aspiration (usually from the sternum or iliac crest) to assess the precursors of blood cells.

• Cytogenetic testing: of the specimen taken from aspirated bone marrow, analyzing the chromosomes to check whether there are alterations present and whether or not the Ph chromosome is present. This chromosome is seen in 95% of cases.

• Fluorescent in situ hybridization (FISH): This test is very similar to cytogenetic testing, though using fluorescent stains. These stains become attached to specific genes or parts of the chromosome, making it possible to determine whether translocation has taken place.

• Polymerase chain reaction (PRC): This is a highly sensitive test that makes it possible to detect certain genetic and chromosomal changes. It is very useful in finding enetic abnormalities in the absence of confirmed chromosomal alterations. This is useful in cases in which Ph chromosome is negative and for subsequent patient follow-up.