BACKGROUND: Fluorescent aerolysin (FLAER) has been recommended as an important part of antibody panel used for flow cytometric detection of paroxysmal nocturnal hemoglobinuria (PNH) clone. This study was aimed to observe the frequency of PNH-positive clones and their sizes in patients screened for various indications. METHOD: A retrospective analysis of 624 patients screened over a period of 30 months. Frequency and size of clone sizes noted, and laboratory parameters were compared among different groups of patient being screened. RESULTS: There were 445 adults and 179 pediatric patients. Indications for screening included AA (n = 433), myelodysplastic syndrome (MDS) (n = 34), hemolytic anemia (n = 84), and thrombophilia workup group (n = 63). PNH clones were found in 39.03%, 5.88%, 26.19%, and 1.59% cases, respectively. No significant difference among adult or pediatric population was noted. The bone marrow failure (BMF) group [AA and MDS] with PNH clone had a significantly lower clone size (Median- 2.7%) as compared to classic PNH group (Median-77.2%). Most of the classic PNH cases (78.26%) and a small proportion of AA (9.9%) showed a large clone size (>50%). In spite of having large clone size, there was a significant difference between the median LDH values of these two groups (2511.5 vs 593 U/L). CONCLUSION: FLAER-based screening detects the presence of PNH clone in a high proportion of AA patients and some MDS patients. These patients usually have a small clone size. Even if they have a large clone, it does not get translated into a high LDH or severe clinical symptoms.
BACKGROUND: Fluorescent aerolysin (FLAER) has been recommended as an important part of antibody panel used for flow cytometric detection of paroxysmal nocturnal hemoglobinuria (PNH) clone. This study was aimed to observe the frequency of PNH-positive clones and their sizes in patients screened for various indications. METHOD: A retrospective analysis of 624 patients screened over a period of 30 months. Frequency and size of clone sizes noted, and laboratory parameters were compared among different groups of patient being screened. RESULTS: There were 445 adults and 179 pediatric patients. Indications for screening included AA (n = 433), myelodysplastic syndrome (MDS) (n = 34), hemolytic anemia (n = 84), and thrombophilia workup group (n = 63). PNH clones were found in 39.03%, 5.88%, 26.19%, and 1.59% cases, respectively. No significant difference among adult or pediatric population was noted. The bone marrow failure (BMF) group [AA and MDS] with PNH clone had a significantly lower clone size (Median- 2.7%) as compared to classic PNH group (Median-77.2%). Most of the classic PNH cases (78.26%) and a small proportion of AA (9.9%) showed a large clone size (>50%). In spite of having large clone size, there was a significant difference between the median LDH values of these two groups (2511.5 vs 593 U/L). CONCLUSION: FLAER-based screening detects the presence of PNH clone in a high proportion of AA patients and some MDSpatients. These patients usually have a small clone size. Even if they have a large clone, it does not get translated into a high LDH or severe clinical symptoms.