Rapid and reliable confirmation of acute promyelocytic leukemia by immunofluorescence staining with an antipromyelocytic leukemia antibody

BACKGROUND: The authors evaluated the utility of immunofluorescence staining with an antipromyelocytic leukemia (anti‐PML) antibody for patients with a suspected diagnosis of new or relapsed acute promyelocytic leukemia (APL) and correlated the findings with the results of other established diagnostic modalities. METHODS: Bone marrow (BM) and/or peripheral blood (PB) smears from 349 patients in whom the diagnosis of APL was considered were assessed with the anti‐PML antibody using immunofluorescence. The study group included 199 patients with confirmed APL and 150 with other conditions. The results of conventional cytogenetics, reverse transcription polymerase chain reaction (RT‐PCR), and fluorescence in situ hybridization (FISH) performed on these patients were correlated with the PML results. RESULTS: Among patients with confirmed APL, anti‐PML antibody was positive in 182 of 184 BM and 32 of 33 PB smears. Conventional cytogenetics demonstrated t(15;17)(q22;q12) in 166 of 182 (91%) patients; 10 had a normal karyotype, 4 had insufficient mitoses to grow in culture, 1 was inconclusive, and 1 was 48, XX, +8, +8. Anti‐PML staining was positive in 9 of 10 with a normal karyotype and in all 4 cases with insufficient mitoses. RT‐PCR and FISH were positive for PML–retinoic acid receptor‐α in 169 of 172 (98%) and 90 of 94 (96%) cases, respectively. Among the patients without APL, 148 of 150 (98.6%) were negative with anti‐PML antibody. The sensitivity and specificity of the test were 98.9% and 98.7%, respectively. CONCLUSIONS: PML immunofluorescence staining is a rapid (