We used RARA FISH at the initial diagnosis (16 cases) and follow-up of APL patients (21 cases) with t(15;17), though RARA FISH was originally designed to detect translocations involving the RARA gene rather than t(15;17), and compared the results with those of PML/RARA FISH.     ///    "In conclusion, we believe that once the PML/RARA rearrangement is confirmed either by G-banding or FISH, RARA FISH is more effective than PML/RARA during the follow-up of APL after treatment.. "    ///    "Although PML/RARA fluorescence in situ hybridization (FISH) can help, the major drawback of FISH is its high false positive rate, which reaches up to 5-10%. "    ///    "By conducting RARA FISH, we were able to significantly resolve the difficulty in interpreting results around cut-off value in PML/RARA FISH. "    ///    A reference range for PML/RARA and RARA FISH was set using 50 normal control specimens.     ///    "Using a RARA split probe, we were able to lower the reference range for RARA rearrangement down to 1.5%, which is significantly lower than that of PML/RARA (8%). "    ///    "Actually 74.2% (46/62 cases) of cases with positive signals of the PML/RARA rearrangement by the PML/RARA probe, showed absolutely negative results with the RARA split probe. "    ///    RARA fluorescence in situ hybridization overcomes the drawback of PML/RARA fluorescence in situ hybridization in follow-up of acute promyelocytic leukemia.. 