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.