Use of flow cytometry in acute promyelocytic leukemia.

Abstract

7075 Background: Acute promyelocytic leukemia (APL) is a highly curable disease, with the majority of failures related to hemorrhagic complications. Hence, rapid diagnosis and early initiation of therapy can drastically prevent these complications and reduce mortality. The current diagnostic strategy utilizing fluorescent in situ hybridization (FISH) is often time-consuming and not readily available in some institutions. This is a review of our institutional experience with the use flow cytometry for diagnosis of APL. Methods: All cases with t(15;17) by FISH and karyotype between 2006 and 2012 were identified. A second group of consecutive cases of non-M3 acute myeloid leukemia (AML) and negative FISH and karyotype for t(15;17) was used for comparison. A total of 21 APL and 42 non-M3 AML cases were analyzed. Results: Both groups were comparable in regard to age, gender, white blood cell count, hemoglobin, blast count and lactate dehydrogenase level. The APL group had significantly higher prevalence of thrombocytopenia, disseminated intravascular coagulation and clinical bleeding at time of admission. Expression of CD11c was lacking in 92.3% (12/13) of APL and 14.6% (6/41) of non-M3 AML cases (p<0.0001). CD34 expression was lacking in 68.4% (13/19) of APL and 42.9% (18/42) of non-M3 AML cases (p=0.06). HLA-DR expression was lacking in 88.9% (16/18) of APL and 9.5% (4/42) of non-M3 AML cases (p<0.0001). Given that APL prevalence is 5% among all AML cases, lack of expression of CD11c, CD34 and HLA-DR have negative predictive values (NPVs) of 99.5%, 97.1% and 9933%, respectively. Among various immunophenotypic profiles, lack of expression of CD11c had the highest NPV (99.5%, p<0.0001) and simultaneous lack of expression of CD11c and HLA-DR had the highest specificity (95.1%, p<0.0001). Conclusions: Expression of CD11c reliably excludes the diagnosis of APL in the majority of AML cases. Flow cytometry has the potential of replacing FISH as the initial test to prompt initiating therapy in APL patients.