CD26 expression on circulating CD34+/CD38‐ progenitor population is a specific and reliable tool for the rapid flow cytometric diagnosis of chronic myeloid leukemia—A single‐center validation study.

Background: Recently, CD26 have been identified as one of the promising and specific marker for the identification of leukemic stem cells (LSCs) in chronic myeloid leukemia (CML). Methods: This was a prospective, observational validation study. Peripheral blood (PB) samples from suspected cases of CML and other hematolymphoid neoplasm were evaluated for the expression of CD26 on stem cells (SC) (CD45 dim/CD34+/CD38‐) fraction by flow cytometry (FCM) using a single tube four‐color antibodies cocktail: CD45‐V500 /CD26‐PE/CD34‐PerCPcy5.5/CD38‐APC‐H7. The diagnosis of CML was confirmed using cytogenetics and/or molecular studies. Additionally, 12 paired PB and bone marrow (BM) samples of CML cases were compared for the proportion of CD26+ LSCs. Results: Expression of CD26 on the SC fraction was invariably noted in all cases (116/116) of CML, irrespective of the disease phase and transcript type. None of other neoplasm (0/26), including the Ph + ALLs expressed CD26. Proportion of SCs expressing CD26 was variable with a median (range) proportion being 61.3% (7.6%–98.6%). Evaluation of paired PB and BM samples showed similar proportion of CD26 + LSCs (R2: 0.969). Conclusion: We confirmed that FCM evaluation of CD26 expression in the PB LSCs is a rapid and specific tool for CML diagnosis. Its utility as a marker for residual disease evaluation can also be explored in the future. [ABSTRACT FROM AUTHOR]