Comparison of flowcytometry‐based scoring system for the diagnosis of early T precursor‐acute lymphoblastic leukemia

Background Early T cell precursor‐acute lymphoblastic leukemia (ETP‐ALL) is a hematolymphoid malignancy where the blasts demonstrate T cell differentiation markers along with stem cell and myeloid antigen expression. The differential diagnosis of ETP‐ALL from non‐ETP ALL and mixed phenotype acute leukemia is often challenging due to its overlapping immunophenotypic picture with co‐expression of myeloid antigens. In this study, we endeavored to describe the immune‐phenotype profile of ETP‐ALL in our patients and compared the utility of four different scoring systems for better discrimination of these entities. Methods This retrospective analysis included 31 ETP‐ALL out of 860 acute leukemia cases consecutively diagnosed at the two tertiary care centers. Flowcytometry‐based immunophenotype was reviewed for all the cases, and the utility of four flow‐based objective scorings was assessed for the diagnosis of ETP‐ALL. Receiver operating curves were drawn to compare the different flow‐based scoring systems. Results The prevalence of ETP‐ALL was 40% (n = 31/77 T‐ALL) in our study group, comprised mainly of adults with a median age of 20 years. The five‐marker scoring system had the maximum area under the curve, followed by the seven‐marker scoring system. A cut‐off of ≥2.5 was more specific (sensitivity: 91%; specificity: 100%), while a score of ≥1.5 was more sensitive but slightly less specific (sensitivity: 94%, specificity: 96%). Conclusion The WHO criteria for the diagnosis of ETP‐ALL should be followed across all laboratories to avoid confusion and for better treatment stratification. Flow‐based scoring systems can be objectively employed for better detection of cases.