Lysis matters: red cell lysis with FACS Lyse affects the flow cytometric enumeration of circulating leukemic blasts.

The whole blood lysis method has become a standard procedure to remove red cells prior to immunophenotypic analysis of leukocytes. In the present study we investigated the influence of four different lysis protocols on the flow cytometric recovery of leukemic blasts. 32 blast cells containing blood samples were stained with anti-CD45 and anti-CD34 monoclonal antibody combinations. Red cell lysis was performed with FACS Lysing Solution and BD PharmLyse™ (Becton Dickinson and Company BD Biosciences, San Jose, CA; n=32) as well as Optilyse C and IOTest 3 (Immunotech SAS, Marseille; n=15 out of 32). Flow cytometric enumeration of blasts was performed on a FACS-Canto flow cytometer. The percentage of blasts after treatment with FACS Lyse was significantly smaller than after PharmLyse™ (p<0.0001), Optilyse C (p<0.0001), or IOTest 3 (p<0.0001), respectively. The difference between PharmLyse™ and Optilyse C (p=0.93), PharmLyse™ and IOTest 3 (p=0.31), and Optilyse C and IOTest 3 (p=0.34) was not significant. These results emphasize the importance of harmonization of red cell lysis protocols for the application of flow cytometry in hematological neoplasms.