Flow cytometry and immunophenotyping of peripheral blood is routinely required to establish a diagnosis of chronic lymphocytic leukemia.
“Flow cytometry and immunophenotyping of peripheral blood demonstrate clonality of the circulating lymphocytes in chronic lymphocytic leukemia (CLL). Absolute lymphocytosis is defined as >5000 cells/mm3. Ninety percent of CLL patients are asymptomatic at the time of diagnosis. Imaging procedures are not necessary for establishing the diagnosis. While a bone marrow biopsy or aspiration and/or a lymph node biopsy may be necessary as the disease progresses, they are not routinely needed to establish a CLL diagnosis.” ABFM
Reference
JAMA 2014;312(21):2265-2276.