Diagnostic Concordance and Superiority of Flow Cytometry Over Immunohistochemistry in Acute Leukemia Immunophenotyping: A Single-Center Study.

BACKGROUND Early diagnosis is crucial for effective treatment and management of acute leukemia. Flow cytometry (FC) is a fast and reliable immunophenotyping technique. This study aimed to compare the diagnostic agreement between FC and histopathological evaluation using shared parameters from bone marrow samples. MATERIAL AND METHODS A total of 144 patients presenting to Adult Hematology, Pediatric Hematology, and Pediatric Oncology clinics at Çukurova University Faculty of Medicine were enrolled; bone marrow samples were processed at the Central Laboratory FC Unit. The cohort included 70 patients with acute myeloid leukemia, 59 with B-cell acute lymphoblastic leukemia, and 15 with T-cell acute lymphoblastic leukemia. The chi-square test, Cohen's kappa, adjusted kappa coefficient, sensitivity, specificity, and accuracy were used to assess FC-IHC concordance. RESULTS The concordance between FC and immunohistochemistry (IHC) was 82.6% for AML (P>0.999, PABAK=0.99) and 61.0% for B-ALL (P=0.054, PABAK=0.89). FC achieved 95% sensitivity for AML and 100% for B-ALL. CD33, MPO, and CD117 showed significant concordance in AML, with sensitivities of 94%, 91%, and 90%, respectively. CD34 was the top-performing biomarker for AML, with 93% sensitivity and 95% specificity. For B-ALL, TdT, CD33, and CD34 showed sensitivities of 77%, 75%, and 81%, respectively. CONCLUSIONS FC showed higher concordance with IHC in AML than in B-ALL and better diagnostic sensitivity for leukemic lineage classification. CD33, MPO, and CD117 were strong AML markers, while TdT, CD33, and CD34 were effective for B-ALL. To quantitatively analyze marker expression with high sensitivity, precise lineage differentiation, and a quick turnaround time, same-day reporting and rapid initiation of targeted therapy make FC essential in modern hematopathology.