IntroductionThe presence of the CD157 GPI-protein on both monocytes and granulocytes only gives opportunity to use it as a target for paroxysmal nocturnal hemoglobinuria (PNH) phenotype cells detection instead of CD24 and CD14, thus improving the technique of PNH-cells evaluation. In present study we used standard technique (International Clinical Cytometry Society (ICCS) guideline proposal) together with 5 color combination of mAbs for detection of PNH-clone on the monocytes and granulocytes simultaneously in one test-tube.Objectives: improvement of PNH cells detection technique.Materials and methods: Blood samples were collected from 37 patients (pts) with bone marrow failure syndrome (aplastic anemia – 34 pts., PNH - 2 pts., myelodysplastic syndrome – 1 pt.; 23 female and 14 men; median age 24 (15 to 66). PNH clone was detected by flow cytometry in all 37 pts. Three healthy donors were in control group.The comparison of the standard 4-color technique of PNH clone size detection on monocytes (FLAER, CD14, CD64, CD45 reagents) and on granulocytes (FLAER, CD24, CD15, CD45 reagents) with the 5-color technique using CD157 GPI-protein antibodies for the both cells populations in one test-tube (FLAER, CD157, CD15, CD64, CD45) were performed.Results: Both methods showed the same high sensitivity for determining of PNH clone. The correlation coefficient was 0,9994 for granulocytes and 0,9924 for monocytes (Figure 1). [Display omitted] In group of patients with minor PNH-clone (range from 0,01% to 0,99%) the clone size was twice times bigger on monocytes compared to granulocytes using the standard method, whereas with antibodies against CD157 this difference disappeared. In patients with PNH-clone between 1% and 10% the clone was nearly three times less on granulocytes than monocytes using both methods; in the group with clone more than 10% there was no differences between cells populations.Table 1Average value of PNH clone on leukocytes in groups of patients both techniquesPNH cloneGr, % (mean)Mon, % (mean)CD24-/FLAER-CD157-/FLAER-CD14-/FLAER-CD157-/FLAER-0%-0,99%0,1780,3490,3230,3781%-9,99%3,983,769,549,98>10%71,5271,5271,8571,34Conclusion: The results of the PNH clone detection obtained with CD157 mAbs are comparable with the standard technique proposed by ISSC. However, the use of CD157 antibodies has important advantage: the PNH clone size detection in one test-tube with 5-color combination reduces time and expenses. Additionally, using of 5-color CD157 antibodies kit would be preferable for the monitoring and detection of minor PNH clone. DisclosuresNo relevant conflicts of interest to declare.