PHA-Induced Peripheral Blood Cytogenetics and Molecular Analysis: a Valid Diagnostic and Follow-up Modality for Acute Promyelocytic Leukemia Patients Treated with ATRA and/or Arsenic Tri-oxide.

Acute promyelocytic leukemia (APML) is characterized by the reciprocal translocation t(15;17) (q22;q12) resulting in the PML-RARα fusion gene. A dual diagnostic and follow up approach was applied including cytogenetic demonstration of the t(15;17) translocation and detection of PML-RARα chimeric transcripts by molecular means.Conventional cytogenetics involving bone marrow is beset with high probability of poor metaphase index and was substituted with phytohemagglutinin (PHA)-induced peripheral blood culture based cytogenetic analysis as a diagnostic and follow up modality in APML patients of Kashmir (North India). Both qualitative (RT-PCR) and quantitative (Q-PCR) tests were simultaneously carried out to authenticate the modified cytogenetics.Patient samples were subjected to the said techniques to establish their baseline as well as follow-up status.Initial cytogenetics revealed 30 patients (81%) positive for t(15;17) whereas 7 (19%) had either cryptic translocation or were negative for t(15;17). Two cases had chromosome 16q deletion and no hallmark translocation t(15;17). Q-PCR status for PML-RARα was found to be positive for all patients. All the APML patients were reassessed at the end of consolidation phase and during maintenance phase of chemotherapy where 6 patients had molecular relapse, wherein 4 also demonstrated cytogenetic relapse.It was found that PHA-induced peripheral blood cytogenetics along with molecular analysis could prove a reliable modality in the diagnosis and assessment of follow up response of APML patients.