The WHO criteria are perhaps most widely used, and define the accelerated phase by the presence of ≥1 of the following haematological/cytogenetic criteria or provisional criteria concerning response to tyrosine kinase inhibitor (TKI) therapy

Haematological/cytogenetic criteria
Persistent or increasing high white blood cell count (> 10 × 109/L), unresponsive to therapy
Persistent or increasing splenomegaly, unresponsive to therapy
Persistent thrombocytosis (> 1000 × 109/L), unresponsive to therapy
Persistent thrombocytopenia (< 100 × 109/L), unrelated to therapy
≥ 20% basophils in the peripheral blood
10―19% blasts in the peripheral blood and/or bone marrow
Additional clonal chromosomal abnormalities in Philadelphia (Ph) chromosome-positive (Ph+) cells at diagnosis, including so-called major route abnormalities (a second Ph chromosome, trisomy 8, isochromosome 17q, trisomy 19), complex karyotype, and abnormalities of 3q26.2
Any new clonal chromosomal abnormality in Ph+ cells that occurs during therapy
Provisional response-to-TKI criteria
Haematological resistance (or failure to achieve a complete haematological response d) to the first TKI
Any haematological, cytogenetic, or molecular indications of resistance to two sequential TKIs
Occurrence of two or more mutations in the BCR-ABL1 fusion gene during TKI therapyThe patient is considered to be in the accelerated phase if any of the above are present. The accelerated phase is significant because it signals that the disease is progressing and transformation to blast crisis is imminent. Drug treatment often becomes less effective in the advanced stages. Blast crisis
Blast crisis is the final phase in the evolution of CML, and behaves like an acute leukemia, with rapid progression and short survival.
Chronic myelogenous leukemia (CML), also known as chronic myeloid leukemia, is a cancer of the white blood cells. It is a form of leukemia characterized by the increased and unregulated growth of myeloid cells in the bone marrow and the accumulation of these cells in the blood. CML is a clonal bone marrow stem cell disorder in which a proliferation of mature granulocytes (neutrophils, eosinophils and basophils) and their precursors is found. It is a type of myeloproliferative neoplasm associated with a characteristic chromosomal translocation called the Philadelphia chromosome. CML is largely treated with targeted drugs called tyrosine-kinase inhibitors (TKIs) which have led to dramatically improved long-term survival rates since 2001. These drugs have revolutionized treatment of this disease and allow most patients to have a good quality of life when compared to the former chemotherapy drugs. In Western countries, CML accounts for 15–25% of all adult leukemias and 14% of leukemias overall (including the pediatric population, where CML is less common). Signs and symptoms
The way CML presents depends on the stage of the disease at diagnosis as it has been known to skip stages in some cases.Most patients (~90%) are diagnosed during the chronic stage which is most often asymptomatic. In these cases, it may be diagnosed incidentally with an elevated white blood cell count on a routine laboratory test. It can also present with symptoms indicative of hepatosplenomegaly and the resulting left upper quadrant pain this causes.