Detection of CD55- and/or CD59-deficient red cell populations in chronic lymphocytic leukemia Egyptian patients

Background: Paroxysmal nocturnal hemoglobinuria (PNH)-phenotype has been described in various hematological disorders, mainly aplastic anemia and myelodysplastic syndromes, while it has been reported that complete deficiency of CD55 and CD59 has also been found in patients with lymphoproliferative syndromes. We aimed to detect frequency and to assess the clinical significancd of the Paroxysmal Nocturnal Hemoglobinuria clones in chronic lymphocytic leukemia patients. Subjects and Methods: The study comprised 70 subjects who were divided into thirty five patients with B-chronic lymphocytic leukemia and thirty five apparently healthy volunteers; anti-CD55 (DAF) and anti- CD59 (MIRL) were conducted using flow cytometry analysis for detection of PNH clone. Univariate analysis and correlations were performed to correlate between the presence of PNH clone and clinical and laboratory parameters. Results: No concomitant negative CD55 and CD59 (CD55- CD59- phenotype) was found among the control group, while it was found in 8 /35 (22%) among the patient group. Isolated CD55 negative (CD55- CD59 + phenotype) was detected in 2/35 (5.7%) and 7/35 (20%) in control group and patient group, respectively. Isolated CD59 negativity (CD55+ CD59 - phenotype) was detected in 2/35 (5.7%) of the control group and 2/35 (5.7%) of patient group also. The PNH clone phenotype was significantly expressed among patient group compared to control group, (p<0.05). According to Binet staging, the median of CD55 negative phenotype in patients group was (11.17%) in stage A, (12.2%) in stage B and (13.8%) in stage C. There was no significant statistical difference between different stages, (P>0.05). While The mean ± SD of CD59 negative phenotype in patient group was (5.40 ±1.30%) in stage A, (9.32 ±3.66%) in stage B and (3.15 ±1.79%) in stage C, There was a highly significant statistical difference between different stages, (P<0.001) . Least significant difference of CD59 negative phenotype among the three stages showed significant elevation in CD59- phenotype in stages A & B compared to stage C, (p<0.05) & (p<0.001) respectively, while there was significant elevation in stage B compared to stage A, (p<0.05). There was a highly significant positive correlation between absolute lymphocytic count with both CD55 and CD59 negative expression, (P < 0.001). Conclusion: From the present study we can conclude that flow cytometry is an important tool which can be used as a screening test for the detection of granulocyte populations deficient for CD55 & CD59 \"PNH phenotype\" in CLL patient. The correlation between the lymphocytic count with PNH phenotype in our study may point to a role for PNH phenotype in the disease progression