Fluorescence in situ hybridization on Peripheral blood for Chronic Myeloid Leukaemia - Rapid and reliable method

Philadelphia chromosome (Ph) is found in more than 95% of Chronic Myeloid Leukaemia (CML) patients arising from the reciprocal translocation of chromosomes 9 and 22 which results in the formation of chimeric fusion gene BCR-ABL. This paved the path for targeted gene therapy in CML and thus plays a pivotal role in diagnosis and prognosis. Fluorescence in situ hybridization (FISH) is a rapid and reliable technique in molecular cytogenetics to detect BCR-ABL fusion signal in both interphase and metaphase spreads of bone marrow sample. Peripheral blood white cells as a surrogate for bone marrow have been suggested by a few studies. The objective of the study was to evaluate FISH on peripheral blood specimen as a rapid and reliable method to quantify Ph positive cells in a patient with Chronic Myeloid Leukaemia. FISH was performed on interphase nuclei from cultured peripheral blood sample of the patient using BCR/ABL Translocation, Dual fusion probe. Chromosomal analysis was performed by GTG banding technique. FISH and karyotyping confirmed the presence of reciprocal translocation t (9; 12) (q34.1; q11.2). Our results confirmed that FISH technique is a rapid, sensitive, quantitative technique which can be used for the evaluation of CML using peripheral blood. In our experience, this situation is usually associated with very high WBC count which can result in increase in the percentage of Phpositive cells.