Immunostaining for Rapid Diagnosis of Acute Promyelocytic Leukemia with the Tetramethylrhodamine-5-Isothiocyanate–Conjugated Anti–Promyelocytic Leukemia Monoclonal Antibody PG-M3

Context.—Anti–promyelocytic leukemia (PML) immunofluorescence staining is a known diagnostic tool for rapid diagnosis of acute promyelocytic leukemia (APL). Objective.—We describe our methods using the recently developed, commercially available, tetramethylrhodamine-5-isothiocyanate–labeled PG-M3 anti-PML antibody for APL testing. Design.—Immunofluorescence staining with the tetramethylrhodamine-5-isothiocyanate–labeled PG-M3 antibody was used to detect PML-RARA in bone marrow aspirate and/or peripheral blood smears from 30 patients with acute leukemia. The results were compared with those of concurrent testing with our in-house polyclonal anti-PML antibody and with established tests. Results.—All APL cases showed a positive (fine/microgranular) immunofluorescence staining pattern, whereas non-APL cases showed a negative (chunky/macrogranular) pattern. These results, which were available within 2 hours, were validated by testing with the polyclonal anti-PML antibody and with established cytogenetic and molecular testing methods. Conclusions.—We validated the utility of the tetramethylrhodamine-5-isothiocyanate–labeled anti-PML antibody PG-M3 for the diagnosis of APL. Our results indicate that immunofluorescence staining with this antibody is a rapid and reliable method for the diagnosis of APL.