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

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.