The triple‐negative (CD34‐/HLA‐DR‐/CD11b‐) profile rapidly and specifically identifies an acute promyelocytic leukemia.

Abstract: Introduction: The genetic testing to confirm or rule out an acute promyelocytic leukemia (APL) typically takes a minimum of 24‐72 hours. Flow cytometric immunophenotyping (FCI) on the other hand provides rapid and objective information to differentiate APL from non‐APL. Methods: FCI features, with single‐tube 8‐color combination using CD45, CD34, HAL‐DR, CD11b, CD13, CD33, and CD117 and CD64, were compared for the 30 consecutive APL and 30 non‐APL acute myeloid leukemia (AML) cases which morphologically mimicked an APL. The diagnosis was confirmed by cytogenetic or molecular genetic testing in the form of t (15:17) (q22; q21)/variant translocations or PML‐RARA fusion transcript analysis. Results: The APL cells lacked CD34, HLA‐DR, and CD11b in 90%, 90%, and 93.3% cases, respectively. Myeloid antigens such as CD33, CD13, CD117, and CD64 were expressed in 96.7%, 96.7%, 76.7%, and 70% cases, respectively. The dual negative profiles, CD34‐/HLA‐DR‐ or HLA‐DR‐/CD11b‐, were noted in 90% and 93.3% cases. The triple‐negative (CD34‐/HLA‐DR‐/CD11b‐) profile was noted in 90% of the cases. The sensitivity, specificity, and positive predictive value (PPV) of CD34‐/HLA‐DR‐ and HLA‐DR‐/CD11b‐ profiles for the diagnosis of APL were found to be 90%, 80% & 81.1% and 93.3%, 86.7%& 87.5%, respectively. Combining the above two profiles resulted in a triple‐negative profile (CD34‐, HLA‐DR‐ and CD11b‐), which had a better specificity (93.3%) and positive predictive value (93.1%), with similar sensitivity. Conclusion: FCI is a rapid and reliable modality for the diagnosis of an APL. The triple‐negative profile (CD34‐/HLA‐DR‐/CD11b‐) rapidly and specifically identifies an APL case. [ABSTRACT FROM AUTHOR]