Apart from the diagnostic and prognostic value of laboratory abnormalities such as clonal lymphocytosis with CD5+CD19+CD23+ phenotype, reduced erythrocyte parameters, thrombocytopenia or bone marrow infiltration by the neoplastic clone as well as low percentage of Gumprecht's shadows, low apoptotic activity of peripheral blood lymphocytes, and increased percentage of CD38- and ZAP-70 ± cells markedly correlate with the stage of disease progression.